كتاب صلاة المسافرين وقصرها
6  
The Book of Prayer - Travellers
(12)
Chapter: It is recommended to pray two rak`ah in the masjid for one who has come from a journey, when he first arrives
(12)
باب اسْتِحْبَابِ الرَّكْعَتَيْنِ فِي الْمَسْجِدِ لِمَنْ قَدِمَ مِنْ سَفَرٍ أَوَّلَ قُدُومِهِ ‏‏
Sahih Muslim 715 c

Jabir b. 'Abdullah reported:

I went with the Messenger of Allah (ﷺ) on an expedition and my camel delayed me and I was exhausted. The Messenger of Allah (ﷺ) thus came earlier than I, whereas I came on the next day and went to the mosque and found him (the Holy Prophet) at the gate of the mosque. He said: It is now that you have come. I said. Yes. He said: Leave your camel and enter (the mosque) and observe two rak'ahs. He (the narrator) said: So I entered and observed (two rak'ahs) of prayer and then went back.
وَحَدَّثَنِي مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، - يَعْنِي الثَّقَفِيَّ - حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ وَهْبِ بْنِ كَيْسَانَ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، قَالَ خَرَجْتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي غَزَاةٍ فَأَبْطَأَ بِي جَمَلِي وَأَعْيَى ثُمَّ قَدِمَ رَسُولُ اللَّهِ صلى الله عليه وسلم قَبْلِي وَقَدِمْتُ بِالْغَدَاةِ فَجِئْتُ الْمَسْجِدَ فَوَجَدْتُهُ عَلَى بَابِ الْمَسْجِدِ قَالَ ‏"‏ الآنَ حِينَ قَدِمْتَ ‏"‏ ‏.‏ قُلْتُ نَعَمْ ‏.‏ قَالَ ‏"‏ فَدَعْ جَمَلَكَ وَادْخُلْ فَصَلِّ رَكْعَتَيْنِ ‏"‏ ‏.‏ قَالَ فَدَخَلْتُ فَصَلَّيْتُ ثُمَّ رَجَعْتُ ‏.‏
Reference : Sahih Muslim 715c
In-book reference : Book 6, Hadith 88
USC-MSA web (English) reference : Book 4, Hadith 1544
  (deprecated numbering scheme)