Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates that Sayyiduna Zayd bin Thabit (may Allah be pleased with him) said: "We ate the pre-dawn meal (suhur) with the Messenger of Allah (peace and blessings be upon him), then we went out for the prayer." I asked: How long was there between the adhan, the iqamah and the suhur? He said: About as long as it takes to recite fifty verses.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4775