Sahih Muslim 1161
صحيح مسلم#1161SahihAbu Dharr reported:I said: Messenger of Allah, which mosque was set up first on the earth? He said: Al-Masjid al-Haram (the sacred). I (again) said: Then which next? He said: It was the Masjid Aqsa. I (again) said: How long the space of time (between their setting up)? He (the Holy Prophet) said: It was forty years. And whenever the time comes for prayer, pray there, for that is a mosque; and in the hadith transmitted by Abu Kamil (the words are):" Whenever time comes for prayer, pray, for that is a mosque (for you)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 5:1