'Swear by the Lord' in the Bible

and I will have you swear by the Lord, God of heaven and God of earth, that you will not take a wife for my son from the daughters of the Canaanites among whom I live,

“Now get up! Go out and encourage your soldiers, for I swear by the Lord that if you don’t go out, not a man will remain with you tonight. This will be worse for you than all the trouble that has come to you from your youth until now!”

So the king summoned Shimei and said to him, “Didn’t I make you swear by the Lord and warn you, saying, ‘On the day you leave and go anywhere else, know for sure that you will certainly die’? And you said to me, ‘The sentence is fair; I will obey.’