Albert Barnes Commentary Luke 1:70

"(As he spake by the mouth of his holy prophets that have been from of old)," — Luke 1:70 (ASV)

His holy prophets, etc. All the prophets are said to have referred to the Messiah, from the beginning of the world. The most striking of these were Jacob (Genesis 49:10); Moses (Deuteronomy 18:15); Isaiah (Isaiah 9:6–7; Isaiah 53:1–12).

Since the world began. This is not to be taken literally, for there were no prophets immediately after the creation. It is merely a general expression, designed to denote that all the prophets had predicted the coming of the Messiah. (Compare Barnes' notes on Luke 24:27.)

(See Barnes' notes on Revelation 19:10.)