Sahih Muslim 438 a
Abu Sa'id al-Khudri reported:
The Messenger of Allah (ﷺ) saw (a tendency ) among his Companions to go to the back, so he said to them: Come forward and follow my lead, and let those who come after you follow your lead. People will continue to keep back till Allah will put them at the back.
حَدَّثَنَا شَيْبَانُ بْنُ فَرُّوخَ، حَدَّثَنَا أَبُو الأَشْهَبِ، عَنْ أَبِي نَضْرَةَ الْعَبْدِيِّ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم رَأَى فِي أَصْحَابِهِ تَأَخُّرًا فَقَالَ لَهُمْ ‏
"‏ تَقَدَّمُوا فَائْتَمُّوا بِي وَلْيَأْتَمَّ بِكُمْ مَنْ بَعْدَكُمْ لاَ يَزَالُ قَوْمٌ يَتَأَخَّرُونَ حَتَّى يُؤَخِّرَهُمُ اللَّهُ ‏"‏ ‏.‏