Sifrei Bamidbar 101

(Bamidbar 12:3) "And the man Moses was extremely humble": "humble" in his mind (i.e., complaisant). You say humble in his mind, but perhaps (the meaning is) "humble" in his wealth; it is, therefore, (to negate this) written (Shemot 11:3) "The man Moses, also, was very great" (in context, in wealth). We find that the second tablets made by Moses were of sapphire, it being written (Devarim 10:1) "Carve out for yourself ([the fragments of the first tablets were vouchsafed to Moses]) two tablets of stone like the first." Just as the first were of sapphire, so, these. And whence is it derived that the first were of sapphire? From (Shemot 32:16) "And the (first) tablets were the work of G-d," and (Ibid. 24:10) "… and under His feet, as the work of a pavement of sapphire." "work" is likened to "work." Just as "work" there (24:10) is of sapphire, so, "work" here (32:16). "more" (humble) than any man on the face of the earth": but not (more humble) than the forefathers. R. Yossi says: Even (more humble) than the forefathers. And what is the intent of than any man on the face of the earth"? — but not (more humble) than the angels.