It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) would place his hands on our shoulders during prayer and say: "Straighten your rows, and do not be uneven, otherwise there will arise discord in your hearts. Let those among you who are wise and intelligent stand close to me, then arrange the rows accordingly, rank by rank." After narrating this hadith, Sayyiduna Abu Mas'ud (may Allah be pleased with him) said: "Today you have fallen into severe disagreements (the reason for which is evident)."