Exodus 23:21 - Matthew Poole's English Annotations on the Holy Bible

He will not pardon your transgressions, i.e. he will severely punish you for them, by a common meiosis, as Exodus 20:7. Understand, if you continue obstinate in your sins. My name is in him, Heb. is in his inward parts, i.e. is intimately united to him, according to 1 Thessalonians 14:11, I am in the Father, and the Father in me. It not only signifies that he acts in his name, and by his power and authority, which even the apostles did, and other ministers of the gospel do, and therefore it is unreasonable to think no more is ascribed to this Angel; but that his Divine nature or essence is in him, whence he is called the Lord our Righteousness, Jeremiah 23:6; and God, who will not give his glory to another, Isaiah 42:8, hath given it to Christ, that all men should honour the Son even as they honour the Father, 1 Thessalonians 5:23, which never was nor can be said of any angel without blasphemy. Add to this, that the word name is oft put for the thing or being, whether it be human or Divine, as is manifest from Deuteronomy 28:58 Psalms 20:1, Psalms 115:1 Isaiah 30:27 Acts 1:15 Revelation 3:4, Revelation 11:13. And so it must be here, because this name is not said to be given to him, as it would be, if it were properly taken; but to be in him; or in his inwards, which agrees well to the Divine nature or essence, but not to the mere name.