Mishkat al-Masabih
Mishkat al-Masabih 1135
The Imam's duty - Section 3
Arabic hadith text
وَعَنِ ابْنِ عُمَرَ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَأْمُرُنَا بِالتَّخْفِيفِ وَيَؤُمُّنَا ب (الصافات)
رَوَاهُ النَّسَائِيّ
Translation
Ibn ‘Umar said
God's Messenger used to command us to be brief, and he would recite as-Saffat (Al-Qur’an; 37) when he was our imam. Nasa’i transmitted it.