عَنْ أَنَسِ بْنِ مَالِكٍ رَضِيَ اللَّهُ عَنْهُ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ: ((رُصُّوا صُفُوفَكُمْ وَقَارِبُوا بَيْنَهَا وَحَاذُوا بِالْأَعْنَاقِ فَوَالَّذِي نَفْسُ مُحَمَّدٍ بِيَدِهِ! إِنِّي لَأَرَى الشَّيَاطِينَ تَدْخُلُ مِنْ خَلَلِ الصُّفُوفِ كَأَنَّهَا الْحَذَفُ))
Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates that the Noble Prophet (peace and blessings be upon him) said: Join your rows, bring them close together, and align your necks (in a straight line). By the One in Whose hand is the soul of Muhammad! Indeed, I see the devils slipping into the gaps between the rows just as if they were black sheep without hair.