John Gill Commentary Exodus 19:3

"And Moses went up unto God, and Jehovah called unto him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel:" — Exodus 19:3 (ASV)

And Moses went up to God
Who was in the pillar of cloud upon the top of the mount; this was on the second day, according to the Targum of Jonathan: "the Lord called to him out of the mountain"; or had called to him, as Aben Ezra, since without his leave he could not have gone up. He called to him out of the cloud upon the top of the mountain to come up, and being come near him, he called to him, and spoke with an articulate voice, as follows:

saying, thus shalt thou say, to the
house of Jacob, and tell the
children of Israel ;
which are the same, and are described as descending from the same person, who was called by both names; the one was his name in the former and lower state of his life, the other in the latter and more prosperous one; and his posterity are called by these two names, as Bishop Patrick observes, to put them in mind, that they who had lately been as low as Jacob, when he went to Padanaram, were now grown as great as God made him when he came from thence, and was called Israel.