What is "tanzil"

Tanzil and Inzal, or "to send down" ( Arabic تنزيل), refers to the act of descent of the pre-existing Qur'an through different Realms.

The process by which Divine message come to the heart of Muhammad is tanzil or nuzul (to come down). As the Qur'an says, "With the truth we(God) have sent it down and with the truth it has come down." It designates positive religion, the letter of the revelation dictated by the angel to the prophet. It means to cause this revelation to descend from the higher world. According to hadith, the verses were sent down in special circumstances which are known as Asbab al-nuzul. However, in this view God himself is never the subject of coming down. The Qur'an asserts that the messenger of Allah(God) is Muhammad.See

• Corbin (1993), p.12
• Wild (1996), pp. 137, 138, 141 and 147

The general acceptance, not necessarily within a Sufi discourse, is that the Qur'an descended firstly (i.e., first Tanazzul) to the Luh Al-Mahfuz (Preserved Scripturum) in an early, unknown or undefined time.

Later on, the Qur'an descended to the cosmic realm in the Laylat al-Qadr (Night of Destiny). This is based on an understanding of sura Al-Qadr:1 as referring to descent of the Qur'an in its entirety. This is backed by `Abd Allah ibn `Abbas "… descended in Ramadan, on the Laylat al-Qadr in one lay down (jumlah, Ar. جملة), …"

In this line of development, the final descent was when the Qur'an was revealed to the Islamic prophet Muhammad by the angel Gabriel.