Leupold Genesis part 48 verse 17, 18

17; 18. And God set them in the firmament of heaven to give light upon the earth and to rule over the day and over the night and to separate the light from the darkness; and God saw that it was good.

Lest anyone be inclined to attribute any other or further purpose to these luminaries, v. 17 reasserts what was stated v. 15b, they are in the expanse of the heavens "to give light upon the earth." It would be a crude interpretation of the opening verb "and he put," if this were understood to mean that God first fashioned the luminaries in one place and then took them and set or suspended them in the firmament. For a literal translation of wayyitten is "and He gave" in the sense of "appointed." Yet the original idea of "to give" is also very appropriate here inasmuch as the luminaries are one of God's good gifts to mankind.