'Solemnly' in the Bible

Visit King David and say to him, 'My master, O king, did you not solemnly promise your servant, "Surely your son Solomon will be king after me; he will sit on my throne"? So why has Adonijah become king?'

Solomon was told, "Look, Adonijah fears you; see, he has taken hold of the horns of the altar, saying, 'May King Solomon solemnly promise me today that he will not kill his servant with the sword.'"

"Note well, you still have to contend with Shimei son of Gera, the Benjaminite from Bahurim, who tried to call down upon me a horrible judgment when I went to Mahanaim. He came down and met me at the Jordan, and I solemnly promised him by the Lord, 'I will not strike you down with the sword.'

So the king sent and called for Shimei and said to him, “Did I not make you swear by the Lord and solemnly warn you, saying, ‘You will know for certain that on the day you depart and go anywhere, you shall surely die’? And you said to me, ‘The word which I have heard is good.’

The king said to him, "How many times must I make you solemnly promise in the name of the Lord to tell me only the truth?"