(Verse 36) - Wonders and signs - Miracles, and remarkable interpositions of God. (See the notes on Acts 2:22).

In the land of Egypt - By the ten plagues. (Exo. 4–12).

In the Red sea - Dividing it, and conducting the Israelites in safety, and overthrowing the Egyptians, (Exo. 14).

In the wilderness - During their forty years’ journey to the promised land. The wonders or miracles were, providing them with manna daily; with flesh in a miraculous manner; with water from the rock, etc., (Exo. 16; Exo. 17; etc).

(Verse 37) - Which said  - (Deut. 18:15, 18). (See this explained, Acts 3:22). Stephen introduced this to remind them of the promise of a Messiah; to show his faith in that promise; and “particularly” to remind them of their obligation to hear and obey him.  The underlying point in all of this is that the Israelites had rejected the word of Moses, their greatest prophet.  Moses had promised, by the inspiration of God, another, greater prophet (fulfilled in the person of Christ).  They had not only rejected Moses, but they also rejected the one he promised would come!

(Verse 38) - In the church - The word “church” means literally “the people called out,” and is applied with great propriety to the assembly or multitude called out of Egypt, and separated from the world. It has not, however, of necessity our idea of a church, but means the “assembly,” or people called out of Egypt and placed under the conduct of Moses.  It is a mistake to equate the two ideas and thus think of OT Israel in terms of the church as we know and understand it.

With the angel - This is undoubted a reference to the giving of the Law on Mount Sinai. Yet that was done by God himself, (Exo. 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; Heb. 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 Rom. 3:2). The word “oracles” here means “commands” or “laws” of God. The word “lively,” or “living” stands in apposition to what is dead, or useless, and means what is vigorous, efficacious; and in this place it means that the commands were of such a nature, and given in such circumstances, as to secure attention; to produce obedience; to excite them to act for God - in opposition to laws which would fall powerless, and produce no effect.

(Verse 39) - Would not obey  - This refers to what they said of him when he was in the mount, (Exo. 32:1, 23).  They would not hear and remain faithful to his command for even just the few days that he was away from them. 

In their hearts turned  - They wished to return to Egypt. They regretted that they had come out of Egypt, and desired again the things which they had there, as preferable to what they had in the desert, (Num. 11:5). Perhaps, however, the expression means, not that they desired literally to “return” to Egypt, but that “their hearts inclined to the habits and morals of the Egyptians.” They forsook God, and imitated the idolatries of the Egyptians.