Types of revelation and Holy Books

"And who believe in the Revelation sent to you (Muhammad), and sent down before you, and they believe with certainty in the resurrection." (Qur'an, 2:4)

According to the Qur'an there are essentially four forms of revelation as listed below in increasing level of significance for human life.

1. Natural Laws: are considered as 'verses of creation', which are commands of God revealed to matter eg, gravitation, "Moreover He comprehended in His design the sky, and it had been (as) smoke: He said to it and to the earth: 'Come ye together, willingly or unwillingly.' They said: 'We do come (together), in willing obedience.'" (Qur'an, 41:11)
2. Animal instincts: All animal instincts are considered to be revelation from God to those animals. For example, the instinct of making honey for a honeybee. "And your Lord inspired the bee, saying: 'take your habitations in the mountains and in the trees and in what they erect. Then eat of all fruits and follow the ways of your Lord made easy (for you).' There comes forth from their bellies, a drink of varying colour wherein is healing for men. Verily in this is indeed a sign for people who think." (Qur'an, 16:68-69)
3. Inspiration to all human beings through human conscience, "It is not fitting for a man that God should speak to him except by inspiration" (Qur'an, 42:51)
4. Formal revelation to an appointed Prophet. This is the highest form of revelation. The above verse continues "or from behind a veil, or by the sending of a messenger to reveal, with God's permission, what God wills for He is Most High, Most Wise" (Qur'an, 42:51)

According to Islam, God has spoken to humanity through divine revelation compiled in holy books of various lengths throughout human history, "Verily, We have inspired you as We have inspired Noah and the Prophets after Him" (Qur'an, 4:163). Some ancient prophets received smaller passages that were less than a book such as about 10 pages revealed to Abraham. As humanity matured larger books were revealed. The four revealed books are mentioned and recognised in the Qur'an are as follows:

1. The Torah to Moses, "It is He Who has sent down the Book (Qur'an) to you (Muhammad) with truth, confirming what came before it. And he sent down the Taurat (Torah) and the Injeel (Gospel)." (Qur'an, 3:3)
2. The Psalms to David. "and to David We gave Zabur (the Psalms)." (Qur'an, 4:163)
3. The Gospel to Jesus (Qur'an, 3:3)
4. The Qur'an to Muhammad (Qur'an, 3:3)

Revelation can take place directly between God and His Prophet as well as through Archangel Gabriel. "Say: Whoever is an enemy to Jibra'il, for indeed he has brought it (this Qur'an) down to your heart by God's permission, confirming what came before it" (Qur'an, 2:97). When revelation came to Prophet Muhammad, he would appear to go in a trance. His body would be heavier then it actually was. According to reports, if he was riding a camel, the camel would have to sit under the weight of the revelation.