Albert Barnes Commentary Acts 7:38

"This is he that was in the church in the wilderness with the angel that spake to him in the Mount Sinai, and with our fathers: who received living oracles to give unto us:" — Acts 7:38 (ASV)

In the church. The word church literally means the people called out. It is applied very appropriately to the assembly or multitude called out of Egypt and separated from the world. It does not, however, necessarily carry our idea of a church, but means the assembly, or people called out of Egypt and placed under the leadership of Moses.

With the angel. In this place, there is an undoubted reference to the giving of the law on Mount Sinai. Yet that was done by God himself (Exodus 20). It is clear, therefore, that by "the angel" here, Stephen intends to designate Him who was God. It may be observed, however, that the law is represented as having been given by the ministry of an angel (in this place) and by the ministry of angels (Acts 7:53; Hebrews 2:2). The essential idea is that God did it by a messenger or by mediators. The character and rank of the messengers, or of the principal messenger, must be learned by looking at all the circumstances of the case.

The lively oracles. (See Romans 3:2, noting the concept of how these oracles were "received"). The word oracles here means commands or laws of God. The word lively, or living (Greek: zwnta), also understood as life-giving, stands in opposition to that which is dead or useless. It means that which is vigorous and efficacious; and in this place, it means that the commands were of such a nature, and given in such circumstances, as to secure attention, produce obedience, and excite them to act for God—in opposition to laws which would fall powerless and produce no effect.