At the beginning of Islam, the number of literates in the whole Mecca was about 17 people (1). In those times, it was even considered as a shame to be able to read or write (2). In the ancient times, people mostly weren’t able to read and literacy was the exclusive privilege of the royal families or rich people. However, in the Arabia, even the royal families couldn’t read or write. Once, Prophet Muhammad (PBUH & HP) wrote a letter to “Bakr ibn Va’il”, a large Arab tribe, and enjoined them to believe in Islam; but when they received the letter, they weren’t even able to read it (3).
In spite of these shameful circumstances, Allah al-mighty sent His most important apostle to the people with only a book as his miracle. The first verses of the Quran, revealed to the Prophet (PUBH & HP), are about reading:
Read in the Name of your Lord who created; (1) created man from a clinging mass. (2) Read, and your Lord is the most generous, (3) who taught by the pen, (4) taught man what he did not know. (5) [96:1-5]

Knowledge and Literacy in Islam

Muslims differentiate between the era before the Messenger (PBUH & HP) and the era after him based on peoples’ knowledge. We call the time before the rise of Islam “The Ignorance era”. 
The holy Prophet (PBUH & HP) taught people that knowledge is the criterion that sets them apart   . The Holy Quran says:
Say, ‘Are those who know equal to those who do not know?’ Only those who possess intellect take admonition (39:9)
About learning, the Holy Messenger (PBUH) says:
 Seek knowledge even if you have to go to China to find it. (4)
Imam Ali (AS) also highlights the Importance of knowledge in his speech with one of his companions:
O Komeil! Knowledge is better than wealth, because knowledge protects you. But for wealth, you have to protect it. Wealth and money get less when you spend them, but by using your knowledge or by teaching it to others you even get more knowledgeable … O Komeil! The ones who love wealth excessively, are like dead people (spiritually) even if they are alive (Physically). However, the spirit of knowledgeable ones will always be alive in the hearts of people even if their bodies are dead. (5)
The Holy Messenger (PBUH & HP) even considered learning as “Vajib” which means that learning is an obligation for every Muslim:
Seeking knowledge is an obligation for every Muslim, men and women (6)
One of the clearest signs that shows the Prophet (PBUH & HP) wanted everybody to be literate and knowledgeable is that he ordered the slaves after the Badr war to teach the children of Medina to read and write and in return, the slaves would be free. (7)

Keeping the Knowledge Safe

The Holy Quran says:
By the pen and what they write (68:1)
We all know that without writing, we weren’t able to communicate our thoughts and ideas with each other and we couldn’t keep them for future generations. In this regard, the Holy Prophet (PBUH & HP) says:
Keep your knowledge safe.
Some people asked:
How can we do that?
The Prophet (PBUH & HP) replied:
By writing it! (8)
Moreover, Imam Sadiq (AS) said to one of his pupils, Mufazzal ibn Umar:
Write and spread your knowledge among the people and if you were going to die, leave your writings for your children because there will be a chaos in the future and in those times, people will not find any peace except in their books (9)
He also said:
Keep your writings because you will need them in the future (10)
Imam Hassan (AS) would gather his children,his niece and nephews and tell them:
You may be considered as kids now, but it is so likely that you will be the elders of many groups and families in the future. Therefore, it is your duty to seek for knowledge. And if there are some people among you who cannot memorize their knowledge, they must write and put their writings in their houses and keep them safe. (11)

Carriers of Books

Action and knowledge are inseparable in the Islamic view. If you act without having enough knowledge and data about the work you’re going to do, you will spoil it and your efforts will be in vain. Imam Sadiq (AS) says:
The one who acts without having enough knowledge is like a passenger who goes on the wrong road. So they get farther and farther from their destination as they go faster and faster. (12)
On the other hand, knowledge without acting is also useless. Imam Ali (AS) says:
Knowledge without action is like a tree without fruit or like a bow without its string (13).
The Holy Quran also says:
The example of those who were charged with the Torah (Old Testament), then failed to carry it, is that of a donkey carrying books. Evil is the example of the people who deny Allah’s signs, and Allah does not guide the wrongdoing lot. (62:5)

Resources

1.  Fotooh al-Boldan, Pg.473
2.   Al-She’r va ash-Sho’ara, Pg.334
3.   As-Sahih fi sirah an-Nabi al-A’zam, Vol.1, Pg.49
4.   Vasa’il al-Shia, Vol.18, Pg.14, number 20 & 23
5.   Nahj al-Balaghah, Utterance no.147
6.   Kafi, vol.1, pg.3
7.   At-Tabaghat al-Kubra, vol.2, pg.22
8.   Bihar al-Anvar, vol.2, pg.151
9.   Kafi, vol.1, pg.52
10.   Kafi, vol.1, pg.52
11.   Kanz al-Ummal, vol.1, pg.752
12.   Tohaf al-Uqul, pg.362
13.   Mizan al-Hikmah, vol.4, pg.2841

Islam considers Praying (Salat) five times a day [1] as one of the most important practical principles. The more times one does something, the more it becomes part of him/her and his/her character; so does prayer. Also, if there were just one prayer a day, people would be more at risk of skipping it by telling themselves: it is only one! Let’s do it tomorrow! But, essentially, why should Muslims perform the daily prayers? Here are some of the answers to this question.

Daily Prayers in Islam (Salat) Help to Be Always Clean

Of the prerequisites of the prayer is the purity of the body from major impurities [i], minor ones [ii], and the purity of clothes and place.  These conditions need a state of physical and spiritual cleanliness to stand before God. So, praying five times a day bounds Muslims to take a bath regularly, wash the face and hands at least five times a day.

These are the practices of personal and public hygiene. According to Prophet Muhammad (PBUH&HP), the prayers act like a river passes nearby one’s house: “If there was a river at your door and you took a bath in it five times a day, would you notice any dirt on you? That is the parable of the five prayers by which Allah removes sins from one’s soul.”[1].

Moreover, several narrations recommend wearing perfume and brushing the teeth before ablution (Wudu) and prayers (Salat) [2,3,4]. These and other narrations, emphasize the importance of appearing clean in public and private.

Daily Prayers in Islam (Salat) Promote Solidarity among Human beings and End Social Rankings

Muslims, all, should pray in the same uniform way, and manner, facing the same direction. No matter what their social position is, where they are on this planet, and what language they speak. This, particularly, means that all human beings are the same before God. Moreover, all the identical acts and words during prayer and positioning towards the same direction, are the practices of promoting solidarity among Muslims, especially when repeated at some times every day.

Becoming Organized by Praying every day

Praying five times a day at certain intervals is an important tool. Since it allows a Muslim to organize his/her day,  be aware of time,  practice and take the control over his/her daily life.

Spiritual Impacts of Daily Prayers in Islam (Salat) 

Becoming more Confident

Much of what we say in our prayers is actually asking for divine help to be righteous in our decisions and actions. And, God has promised in the Quran to respond to whoever that calls him (40:60). This gives a good feeling. Knowing that a kind, wise and superior power hears us and will help us through the hard moments. He also makes us more confident and determined in our decisions.

Inner Peace

Just as we need food to meet our physical needs, Islam teaches us to pray and worship to get the food for our souls. That is inner peace and tranquility.

Fewer Errors and Sins

One of the main objectives of daily prayers (Salat) is to remember God. It also helps to purify ourselves and keep away all the evil thoughts and actions. "Indeed, prayer prohibits immorality and wrongdoing ... And Allah knows that which you do." (29:45).

Prophet Muhammad (PBUH&HP) said that Satan is afraid of the faithful Muslim who performs the prayers (Salat) in their right times. Once a Muslim forgets to do the prayer at the right time, Satan becomes encouraged to tempt him/her to do great sins [5].

If we once do wrong to someone, we will be ashamed of him/her, or we do not even dare to face him/her the next time we meet. Prayer has the same effect. It is the confrontation of one's conscience, knowing that nothing can be hidden from God, whether manifested or concealed. Then, it becomes more difficult to commit evil deeds when we have to stand five times a day in front of God who knows every detail about us.

Remembering the Philosophy of Life

Another purpose of prayer for a Muslim is to remember. At fixed intervals, no matter how busy a Muslim is, he/she might ask himself, “OK, why am I here, what do I do in this world?” Also, prayer helps Muslims to be accountable for their daily actions which greatly change their perceptions of life.  

On top of everything, worshiping God is the purpose for which the humankind was created: “And I did not create the jinn and mankind except to worship Me.” (51:56).

Last but not least, what do we usually do to one who has done a favor to us? The answer is: try our best to compensate, or at least to thank him/her even several times. Now, how can we compensate the blessings that God has given us? It is not possible! Then, we pray to thank Him for all the wonderful, beautiful blessings that He has given us. Although we do not deserve many of them.

Notes:

[i] Can be removed by ritual bathing (Ghusl)

[ii] Can be removed by ablution (Wudu)

References:

1. Ibn Babawayh, “Man la yahduruhu al-Faqih”, vol.1, p. 316.
2. M. al-Kulaynī, “Al-Kafi”, vol. 5, p. 511.
3. M. al-Kulaynī, “Al-Kafi”, vol. 5, p. 515.
4. Ibn Babawayh, “Al-Khisal”, p. 481.
5. Ibn Babawayh, “Uyun akhbar al-Rida”, ch. 30, T. 21.