This expression 'to crawl' is used to illustrate the high merit of praying 'Isha and Fajr in congregation in the mosque. This Hadith also urges to make best to occupy the first rows, as the 'Angels of Mercy' pray for the Imam first, then for those who pray immediately behind him in the first row, then those behind them, and so on. The Hadith also points out the excellence of Adhan and the great reward of the person who pronounces it.