Surah 26. Ash-Shuara, Ayah 194

According to almost all the classical commentators, the expression ar-ruh al-amin (lit., "the faithful [or "trustworthy"] spirit") is a designation of Gabriel, the Angel of Revelation, who, by virtue of his purely spiritual, functional nature, is incapable of sinning and cannot, therefore, be other than utterly faithful to the trust reposed in him by God (cf. 16:50 ). On the other hand, since the term ruh is often used in the Qur'an in the sense of "divine inspiration" (see surah {2}, note [71], and surah {16}, note [2]), it may have this latter meaning in the above context as well, especially in view of the statement that it had "alighted from on high upon the heart" of the Prophet.

Qalb (Heart) signifies not only the seat of the affections, but also the seat of the memory and understanding. The process of inspiration is indicated by the impression of the divine Message on the inspired one's heart, memory, and understanding, from which it was promulgated in human speech to the world. In this case the human speech was the perspicuous Arabic tongue, which would be plainly intelligible to the audience who would immediately hear it and be through them transmitted to all the world.