Though the whole passage is but a continuation of the same blessed discourse, in which God himself is the speaker; yet I stop the Reader under these two verses, to remark the peculiarity of what is said. If Jesus, under the spirit of prophecy, be here delivering these gracious truths to the Church, (as I think cannot be questioned) then will it follow, that all the three persons of the Godhead are here introduced as engaged in this blessed sermon. Jesus opened his gospel, and spoke not in secret, but openly to the people: so he received his commission, Isaiah 6:8-10; and so, in the synagogue, he declared the Spirit of Jehovah to be upon him; compare Isaiah 61:1, etc. with Luke 4:18, etc. And if Jehovah and his Spirit (as in those verses is said to have been the case) be thus sent, who will not see, as in the baptism of Jesus, all the three persons of the Godhead engaged in this act of grace, Matthew 3:16-17.
Related Commentaries of Isaiah 48:15
Isaiah 48:15-16
15 I, even I, have spoken; yea, I have called him: I have brought him, and he shall make his way prosperous.
16 Come ye near unto me, hear ye this; I have not spoken in secret from the beginning; from the time that it was, there am I: and now the Lord GOD, and his Spirit, hath sent me.