In the old testament scriptures the Psalm reads “The LORD said to my Lord...” King David was told his son would be the son of God who would build the temple. Jesus is the Lord of David and David is the father of the one who builds the temple. So Jesus is the Head of the temple. And Jesus’ temple is the body of those who truly follow Him. This was all know prophetically to King David when he wrote those words and as told by God about his son. So it is all predetermined. Jesus simply clarified that it is all predetermined even before Abraham was born and before creation was created. And it all existed in those ancient times because David called Jesus “my Lord” centuries before Jesus came in the flesh, so it was already a reality back then. He said it past tense and present tense. Centuries BC.
