Prayer in Islam (Salat) is one of the most important practical principles of Islam [1]. It is a physical, mental and spiritual act of worship consisting of prescribed actions and words. Every action in the prayer in Islam (Salat) is meaningful and if you want to know the Philosophy of Prayer in Islam,  we will see what each movement in the prayer means and represents.

The Philosophy of Prayer in Islam

Standing (Qiyam)

The prayer in Islam starts with standing. That is to appear in front of God gently and courtly with your whole heart and body; that is how one demonstrates the respect for others. Having the gaze down in Qiyam demonstrates the modesty towards God. It makes one forget about his\her superiority and helps to overcome his\her arrogance [2]. Also, knowing that one should stand five times a day in front of a superior power, who knows every overt and covert act and behavior, will eventually prevent from evil deeds and sins [2].    

Intention (Niyyah) of the Prayer in Islam

We do many things every day, some of which are repetitive and by habit, and we are not even aware of why we are doing them. Prayer in Islam, one of those works, seems to be a physical practice. That is why the prayer must have a Niyyah to prevent the prayer from becoming a daily habit and to help the Muslim to recall the reason behind that. Hence, a prayer without Niyyah will be a set of physical movements, and it won’t be accepted.  

Niyyah reminds one that he\she is showing up to demonstrate the submission to the divine orders. Having a pure intention in the prayer teaches to avoid duplicity. It is not necessary to repeat the words of the Niyyah. That is enough to recall it and to consider it throughout the prayer. Indeed, this should be considered during any other act or practice in daily life; firstly, to purify our intentions for God; then, to stick to that intention until the end.

Takbir   

The sayings in the prayer in Islam (Salat) start with Takbir. Takbir means to regard God as great. By saying Takbir, we express our belief that God is great. There exists nothing similar to Him. He cannot be perceived or touched by our physical senses and understanding [3]. Takbir reminds us of the Monotheism (Tawhid) which is the first pillar of Islam [4]. 

Bowing (Ruku)

Bowing (Ruku) is a perfect demonstration of the gratitude and respect that a human being has for God, as a divine source and a higher power. And, this is a unique posture that a Muslim will never have in front of anyone else [5]. In Ruku, every individual, in whatever position and grade, bows to God which consequently reduces the arrogance and pride within him\her. Lady Fatima (AS) said: “God has ordered […] the prayer to purify you from arrogance and pride” [6]. 

According to Imam Ali (AS), holding the neck straight during Ruku shows that one believes firmly in Islam such that he\she won’t give up even if he loses his\her life (to have the neck cut) for this belief. Another point in Ruku is that it is a unique posture that only exists in the Islamic ritual and distinguishes the Islamic prayer.   

Prostration (Sujood)

Prostration (Sujood) is exhibiting the maximum humility and dignity for God. Imam Sadiq (AS) describes that one is closest than ever to God in this posture [7]. According to the Quran: “to Allah prostrates whatever is in the heavens and whatever is on the earth of creatures…” (16:49). This means that in that posture, the human being is in harmony with the whole universe and creatures. 

Imam Ali (AS) explained that the first Sujood means that God has created us from the earth. Coming up from the first Sujood is the symbol of this worldly life. The second Sujood represents the death and returning to the earth. Finally, rising from the second Sujood symbolizes the afterlife [8]. According to the interpreters of the Quran, this refers to the fact that: “From the earth, We created you, and into it, We will return you, and from it, We will extract you another time” (20:55). 

The Prayer in Islam, Beneficial to Soul as Well as Body

There have been some attempts in the recent years to analyze and justify the physical benefits of performing the prayer. Those discussions might be true, but they are not the whole reason behind this practical principle of Islam. The prayer is a means of worship that engages the body and soul and is beneficial to both. The reasons above are a small part of the philosophy behind the acts of the prayer. One might refer to the advanced references for more details. 

References:

1. Shaikh al-Hur al-Aamili, "Wasail al-Shia", p. 214.
2. J. Maleki Tabrizi, “The Mysteries of the Prayer”, vol. 1, p. 323.
3. Ibn Babawayh, "Man la yahduruhu al-Faqih", Book Salat, Chap. 17
4. Monotheism Tawhid
5.  A. Hosseini Khamenei, “The Prayer in Depth”, p. 5.
6. M. Majlisi, "Bihar al-Anwar", vol. 29, p. 223.
7. Shaykh al-Kulayni, "al-Kafi", vol. 3, p. 324, T. 11.
8. Ibn Babawayh, "Man la yahduruhu al-Faqih", vol. 1, p. 311.

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