Anas (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "Fill (complete) the first row, then the one next to it; and if there is any deficiency (incompleteness), it should be in the last row."[Abu Dawud]. (RU)
App reference (RU): Book 9, Hadith 103 (RU)
Arabic/English book reference (RU): Book 9, Hadith 1093 (RU)