It is narrated from Hazrat Nafi that Sayyiduna Umar bin Khattab (may Allah be pleased with him) used to order the people to straighten the rows, and when the people informed him that the rows had been straightened, he would then say the takbeer.

It is narrated from Malik bin Abi Amir Asbahi that I was with Sayyiduna Uthman bin Affan (may Allah be pleased with him), when the call for prayer (takbeer) was made, and I continued talking to him, because I wanted him to assign me some stipend, and he was straightening pebbles with his shoes, until those people arrived who were appointed to straighten the rows, and they informed him that the rows had been straightened. Then he said to me: Join the row, and then he said the takbeer.