Volume 4, Book 55, Number 585:
Narrated Abu Dhar:
I said, “O Allah’s Apostle! Which mosque was first built on the surface of the earth?” He said, “Al-
Masjid-ul-,Haram (in Mecca).” I said, “Which was built next?” He replied “The mosque of Al-Aqsa
( in Jerusalem) .” I said, “What was the period of construction between the two?” He said, “Forty
years.” He added, “Wherever (you may be, and) the prayer time becomes due, perform the prayer
there, for the best thing is to do so (i.e. to offer the prayers in time).”