C. F. Keil and Franz Delitzsch on Exodus 4:20

Exo 4:20

Moses then set out upon his journey, with his wife and sons. בּניו is not to be altered into בּנו, as Knobel supposes, notwithstanding the fact that the birth of only one son has hitherto been mentioned (Exo 2:22); for neither there, nor in this passage (Exo 4:25), is he described as the only son. The wife and sons, who were still young, he placed upon the ass (the one taken for the purpose), whilst he himself went on foot with “the staff of God” - as the staff was called with which he was to perform the divine miracles (Exo 4:17) - in his hand. Poor as his outward appearance might be, he had in his hand the staff before which the pride of Pharaoh and all his might would have to bow.