Abu Hurairah (May Allah be pleased with him)reported:
The Messenger of Allah (ﷺ) said, "Let the Imam stand in the middle (so that those praying behind him should be standing both on his right and his left) and close the gaps."[Abu Dawud]. (JA)
App reference (JA): Book 9, Hadith 106 (JA)
Arabic/English book reference (JA): Book 9, Hadith 1096 (JA)