The Messenger perceived a tendency among his Companions to stand in the back rows, and he said to them: Come forward and be close to me and let those who come after you, follow your lead. If people continue to fall behind, Allah puts them behind. [Muslim]

أن رسول الله رأى في أصحابه تأخُّرًا فقال لهم: «تَقَدَّمُوا فَأْتَمُّوا بي، وليأتمَّ بكم مَن بعدكم، لا يزال قومٌ يتأخرون حتى يؤخرَّهم اللهُ». (مسلم)