Sahih Muslim Book - 5, Hadith - 1467

وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِى شَيْبَةَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ عَنْ شُعْبَةَ عَنْ أَبِى عِمْرَانَ عَنْ عَبْدِ اللَّهِ بْنِ الصَّامِتِ عَنْ أَبِى ذَرٍّ قَالَ إِنَّ خَلِيلِى أَوْصَانِى أَنْ أَسْمَعَ وَأُطِيعَ وَإِنْ كَانَ عَبْدًا مُجَدَّعَ الأَطْرَافِ وَأَنْ أُصَلِّىَ الصَّلاَةَ لِوَقْتِهَا « فَإِنْ أَدْرَكْتَ الْقَوْمَ وَقَدْ صَلَّوْا كُنْتَ قَدْ أَحْرَزْتَ صَلاَتَكَ وَإِلاَّ كَانَتْ لَكَ نَافِلَةً ».

It was narrated that Abu Dharr said: "My beloved (i.e., The Prophet (s.a.w)) advised me to listen and obey, even if the one appointed over me is a slave with his hands and feet cut off, and to offer the prayer on time. 'If you catch up with the people but find that they have already prayed, then you will have preserved your prayer, and if you do catch up with them, that will be a voluntary prayer for you."'