Moses was loyal to the oath he had given his father-in-law Jethro, never to return to Egypt without securing his consent. His first concern therefore was to go back to Midian and obtain his permission, which Jethro gave freely. Then Moses could set out on his journey. He tarried only to take his wife and his children with him, which made his father- in-law say, "Those who are in Egypt are to leave it, and thou desirest to take more thither?" Moses replied: "Very soon the slaves held in bondage in Egypt will be redeemed, and they will go forth from the land, and gather at Mount Sinai, and hear the words, 'I am the Lord thy God,' and should my sons not be present there?" Jethro acknowledged the justice of Moses' words, and he said to him, "Go in peace, enter Egypt in peace, and leave the land in peace."[143] At last Moses sallied forth upon his journey to Egypt, accompanied by his wife and his children. He was mounted upon the very ass that had borne Abraham to the Akedah on Mount Moriah, the ass upon which the Messiah will appear riding at the end of days.[144] Even now, his journey begun, Moses was but half-hearted about his mission. He travelled leisurely, thinking: "When I arrive in Egypt and announce to the children of Israel that the end of the term of Egyptian slavery has come, they will say, 'We know very well that our bondage must last four hundred years, and the end is not yet,' but if I were to put this objection before God, He would break out in wrath against me. It is best for me to consume as much time as possible on the way thither." God was ill pleased with Moses for this artifice, and He spake to him, saying, "Joseph prophesied long ago that the oppression of Egypt would endure only two hundred and ten years." For his lack of faith Moses was punished while he was on the road to Egypt.[145] The angels Af and Hemah appeared and swallowed his whole body down to his feet,[146] and they gave him up only after Zipporah, nimble as a "bird,"[147] circumcised her son Gershom, and touched the feet of her husband with the blood of the circumcision. The reason why their son had remained uncircumcised until then was that Jethro had made the condition, when he consented to the marriage of his daughter with Moses, that the first son of their union should be brought up as a Gentile.[148] When Moses was released by the angels, he attacked them, and he slew Hemah, whose host of angels, however, held their own before the assailant.[149] The Divine voice heard by Moses in Midian telling him to return to his brethren in Egypt fell at the same time upon the ear of Aaron, dwelling in Egypt, and it bade him "go into the wilderness to meet Moses." God speaketh marvellously with His voice, and therefore the same revelation could be understood one way in Midian and another way in Egypt.