Abu al-Qasim al-Jadali says: I heard Sayyiduna Nu'man bin Bashir (may Allah be pleased with him) saying: the Messenger of Allah (peace and blessings be upon him) turned his blessed face towards us and said three times: "Straighten your rows. By Allah, you will surely straighten your rows, or else Allah Almighty will put discord between your hearts." The narrator says: I saw a man pressing his ankle against the ankle of his companion, his knee against the knee of his companion, and his shoulder against his shoulder.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 357