Answer
(Fatwa: 1477/1126/B=1433)
Madarij al-Nabuwah is an authentic and reliable book. It was written by the grand scholar and Muhaddith Hadhrat Maulana Abdul Haque Muhaddith Dehlavi (رحمة الله عليه). It is written on page 17 of the book that the holy Prophet Muhammad (صلى الله عليه وسلم) did not drink water immediately after having food. The same is also written in Shamail Kubra, Vol 1, p 173, with the reference of this book. However our Shaikh Hadhrat Maulana Zakaria (رحمة الله عليه) says that one should drink some water in the middle of meal so that the context of the dua [الحمد لله الذي اطعمنا وسقانا وجعلنا مسلمين] which is recited after having meal could apply as the dua means: All praise is for Allah who has fed us, given us drink and made us amongst the Muslims.
As per the views of physicians and doctors it makes the food part of the body and keeps the system of stomach accurate, and one remains away from cold, influenza and gastric problems etc. One should drink water after half an hour or 45 minutes of food.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband