The Trinity and OT

http://christianthinktank.com/trinity.html

https://christiandefense.org/oneness/the-trinity-in-the-old-testament/

https://carm.org/verses-showing-plurality-god-old-and-new-testaments

https://ichthys.com/mail-one%20true%20God.htm

https://overviewbible.com/trinity-bible-verses/