Origen of Alexandria : Moses, when he had come to the place that God showed him, is not permitted to ascend, but before that it is said to him: "loose the strap of the sandal from your feet." To Abraham none of these things is said, nor to Isaac, but they ascend and do not put off their sandals. In which perhaps this is the reason: that Moses, although he was "great," yet was coming from Egypt, and there were certain bonds of mortality knotted to his feet. But Abraham and Isaac have none of these things, but come to the place. — HOMILIES ON Genesis 8.7 Origen of Alexandria : About Isaac it is said that "he grew strong until he became great, exceedingly great." Moses was called "great," and John the Baptist was called "great," and now Jesus is called "great," and after this no one is any longer called "great." For before he who is truly "great" had come, in comparison with the rest of men, the saints whom we mentioned earlier were called "great." — HOMILIES ON Leviticus 12.2.5