Abu al-Zahiriyyah narrates from Abu Shajarah, and he from Kathir bin Murrah, and he did not mention Sayyiduna Ibn Umar (may Allah be pleased with them both), that the Messenger of Allah (peace and blessings be upon him) said: "Straighten the rows, align the shoulders, fill the gaps, be gentle in the hands of your brothers, and do not leave gaps for the devils. Whoever joins a row, Allah will join him; and whoever breaks a row, Allah will cut him off."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5186