Fruit of Paradise
In verse (25:48) the water which comes down from heaven is called “ṭahūr” which means “very pure”. By this water is meant the knowledge of the Holy Prophet which appears from his Bāb (gate), namely, the true Imām. For the rain of knowledge which poured down from the heaven of Prophethood has turned into reservoirs in the mountain of Imāmat, just as the worldly mountain stores rain and snow on its exterior and in its interior and preserves them in their original state. Thus, to those who live close to this blessed mountain, this very pure water of religious knowledge is always available to purify the soul and intellect. In verse (76:21) it is said that God will give a pure drink (sharāban ṭahūrā) to the people of Paradise. As has already been mentioned, by this is meant true (esoteric) knowledge.
This excerpt has been taken from page 70.