The Messenger of Allah ﷺ said, "Straighten the rows, for you are arranging yourselves in the manner of the rows of the angels. Align your shoulders, fill the gaps, be gentle in the hands of your brothers, and do not leave openings for the devil. Whoever joins a row, Allah will join him, and whoever breaks a row, Allah will cut him off."
حدثنا هارون بن معروف حدثنا عبد الله بن وهب عن معاوية بن صالح عن أبي الزاهرية عن كثير بن مرة
أن رسول الله ﷺ قال أقيموا الصفوف فإنما تصفون بصفوف الملائكة وحاذوا بين المناكب وسدوا الخلل ولينوا في أيدي إخوانكم ولا تذروا فرجات للشيطان ومن وصل صفا وصله الله تبارك وتعالى ومن قطع صفا قطعه الله
Its isnad is sahih. Muawiya bin Salih bin Hudayr, the ha vowelized with damma and the dal vowelized with fatha, both being undotted letters, Hadrami Himsi, was one of the prominent scholars and a judge of Andalus. He is reliable, deemed trustworthy by Ahmad, Ibn Main, and others. Whoever criticized him did so without proper justification.Muhammad bin Wadah said, Yahya bin Main said to me, "Have you gathered the hadith of Muawiya bin Salih?" I said, "No." He said, "What prevented you from that?" I said, "He settled in a land whose people at that time were not people of knowledge." He said, "By Allah, you have lost a great deal of knowledge."Bukhari gave his biography in Tarikh al-Kabir 1/4/335, and said, Ali (meaning Ibn Madini) said, "Abdul-Rahman (meaning Ibn Mahdi) considered him trustworthy, and said, 'He settled in Andalus, and he was originally from Hims.'" He said something similar in Tarikh Saghir 192, 193. He also has a good biography in Tarikh Qudat Qurtuba by Muhammad bin Harith Khushani, pages 30–43.Among what is mentioned there, Ahmad bin Khalid recounted, saying, "The commander Abdul-Rahman, may Allah have mercy on him, sent Muawiya bin Salih to Syria, and he performed hajj during that journey. When he entered Masjid al-Haram during the days of the pilgrimage season, he saw there the study circles of the people of hadith, Abdul-Rahman bin Mahdi, Yahya bin Saeed Qattan, and others of their peers. He went to a pillar and prayed two units of prayer, then turned to discuss with those who were with him, and they mentioned some hadiths. Muawiya bin Salih said, 'Abu Zahiriya Judayr bin Kurayb narrated to me, from Jubayr bin Nufayr, from Abu Darda, from the Messenger of Allah ﷺ...' Some of the people in that circle heard what he said, and they said, 'Fear Allah, old man, and do not lie! There is no one on the face of the earth who narrates from Abu Zahiriya, from Jubayr bin Nufayr, from Abu Darda, except a man who settled in Andalus called Muawiya bin Salih.' He said to them, 'I am Muawiya bin Salih.' Then all the circles broke up, and everyone gathered around him, and they wrote down from him during that pilgrimage season a great deal of knowledge."Abu Zahiriya, Judayr bin Kurayb, and Kathir bin Mura were both previously confirmed as reliable in 4880.Abu Dawud narrated the hadith (1:251) via Ibn Wahb with this isnad connected, and also via Layth bin Saad from Kathir bin Mura as a mursal report, not mentioning Ibn Umar in it. His version is slightly abridged, not including the statement, "For you are forming rows like the rows of the angels."Nasai narrated only its end, "Whoever joins a row, Allah will join him, and whoever breaks a row, Allah will break him" (1:131), via Ibn Wahb with this isnad, connected.Likewise, Hakim narrated it in Mustadrak (1:212) via Ibn Wahb, connected and abridged, but with Abdullah bin Amr instead. I consider this most likely a copyist's or printer's error, especially since Suyuti mentioned it in Jami Saghir (9076) and attributed it to Mustadrak from the hadith of Ibn Umar, as it appears here and in the rest of the sources.Khalal, with fatha on the kha and the lam, means the gap between two things, and its plural is khilal, like jabal and jibal.Abu Dawud said, the meaning of "and be soft in the hands of your brothers" is, when a man comes to the row intending to enter it, each man should relax his shoulders for him so that he may enter the row. This explanation by Abu Dawud is the sound, good, and clear one, contrary to what Ibn Athir explained regarding the hadith of Ibn Umar, "The best of you are those with the softest shoulders in prayer," where he said it is the plural of alyan, meaning stillness, dignity, and humility!! This is a far-fetched and unconvincing interpretation.Furajat, with two dammas, is the plural of furja, with damma on the fa and sukun on the ra. Ibn Athir said it refers to the gaps that occur between worshippers in the rows. He attributed them to Satan as an emphasis on their seriousness, and to encourage caution against them.