The Prophet of Allah ﷺ said, "Straighten your rows, draw them close together, and align your necks. By the One in whose hand is the soul of Muhammad, I see the devils slipping through the gaps in the row like little black sheep."
أخبرنا محمد بن عبد الله بن المبارك المخرمي قال حدثنا أبو هشام قال حدثنا أبان قال حدثنا قتادة قال
أن نبي الله ﷺ قال راصوا صفوفكم وقاربوا بينها وحاذوا بالأعناق فوالذي نفس محمد بيده إني لأرى الشياطين تدخل من خلل الصف كأنها الحذف
[Its chain of transmission is sahih] Abu Dawud reported it in the Book of Prayer, chapter on straightening the rows, hadith 667, from the hadith of Abu Aban bin Yazid Attar with this chain. It is also found in Kubra, hadith 889. Ibn Khuzayma graded it sahih, hadith 1545, as did Ibn Hibban, hadiths 387 and 391.