John Gill Commentary 1 Samuel 20:14

"And thou shalt not only while yet I live show me the lovingkindness of Jehovah, that I die not;" — 1 Samuel 20:14 (ASV)

And you shall not only, while yet I live, show me the
kindness of the Lord
Such kindness as is well pleasing in the sight of God, and imitate what he shows to men, and which was covenanted, promised, and agreed to in the presence of the Lord, when David and Jonathan entered into covenant with each other; this Jonathan did not doubt of, and therefore did not make this a request:

that I die not ;
he had no fear nor dread on his mind, should David come to the throne while he was alive, that he would take away his life; which was usually done by tyrants and usurpers, when there were any that had a fairer title, and better claim to the throne than they.