It was narrated from Al'Irbad bin Sariyah that the Messenger of Allah (ﷺ) used to send Salah on the first row three times and on the second row once.
Sunan an-Nasa'i Book 10, Hadith 41
← Previous Hadith "The Messenger of Allah (ﷺ) came out to us and said:'Will you not form rows as the angels form rows before their Lord? They said: 'How do the angels form rows before their lord? He said: 'They complete the first row and fill the gaps in the rows."'

Sunan an-Nasa'i Book 10, Hadith 40 Next Hadith → "Complete the first row, then the one behind it, and if any row is to be left incomplete let it be the last row."

Sunan an-Nasa'i Book 10, Hadith 42