All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It is confirmed that it is desirable to drink Zam Zam water after praying two Rak’as when finishing the circumambulation around the Ka’bah and before Sa'y (going between Safaa and Marwah). The evidence is what Imaam Ahmad reported that Jaabir Ibn ‘Abdullaah narrated that the Prophet made circumambulation around the Ka’bah, quickening his steps in the first three rounds, and after completing the Tawaf, he prayed two Rak’as. Then he went to Zam Zam well and drank from it, and poured some water over his head. Then he returned again to the black stone and touched it, and then went to Safaa, and said: “We begin with what Allaah had began”, referring to verse 158 of chapter Al-Baqarah. [2:158]
Allaah knows best.