Acts 7:30
"Then after [another] forty years passed, an angel appeared to him [one day] out of a flaming bush in the wilderness near Mt. Sinai.
Acts 7:38
This is the man who was with our forefathers and with the assembly [of Hebrews] in the wilderness [after] the angel had spoken to him at Mt. Sinai. He [is the one] who received the living messages [from God at Mt. Sinai] and gave them to us.
Galatians 4:24
This set of circumstances contains an illustration; for these two women [Hagar and Sarah] represent the two Agreements [between God and mankind]. The one [Agreement], given at Mount Sinai, represents Hagar, whose children became [the Israelites], enslaved under bondage [to the requirements of the law of Moses].