صَحِيحُ مُسْلِمٍ
Sahih Muslim 715 a
The Book of Prayer - Travellers
It is recommended to greet the masjid by praying two rak`ah, and it is disliked to sit before praying these two rak`ah, and this is prescribed at all times
حَدَّثَنَا أَحْمَدُ بْنُ جَوَّاسٍ الْحَنَفِيُّ أَبُو عَاصِمٍ، حَدَّثَنَا عُبَيْدُ اللَّهِ الأَشْجَعِيُّ، عَنْ سُفْيَانَ، عَنْ مُحَارِبِ بْنِ دِثَارٍ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، قَالَ كَانَ لِي عَلَى النَّبِيِّ صلى الله عليه وسلم دَيْنٌ فَقَضَانِي وَزَادَنِي وَدَخَلْتُ عَلَيْهِ الْمَسْجِدَ فَقَالَ لِي صَلِّ رَكْعَتَيْنِ .
Jabir b. 'Abdullah reported: The Messenger of Allah (ﷺ) owed me a debt; he paid me back and made an addition (of this). I entered the mosque and he (the Prophet) said to me: Observe two rak'ahs of prayer.
Sahih Muslim, 715 aSahihصحيح