The statement:

"Let peoples serve you, and nations bow down to you..."

…was made by Isaac when he was blessing his son Jacob, believing he was blessing Esau (Genesis 27:29). This blessing was part of the patriarchal blessing meant for the firstborn. Rebekah helped Jacob deceive Isaac into receiving this blessing.

Reference (RSV – Genesis 27:29):

“Let peoples serve you,
and nations bow down to you.
Be lord over your brothers,
and may your mother’s sons bow down to you!”