NET
30 So then, because he was a prophet and knew that God had sworn to him with an oath to seat one of his descendants on his throne,
Darby
30 Being therefore a prophet, and knowing that God had sworn to him with an oath, of the fruit of his loins to set upon his throne;
KJV
30 Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne;