This verse begins in Hebrew with the common conjunction. Here it functions to mark a contrast between what David wanted to do (verse 17) and what God intended, so it is correctly translated But in Revised Standard Version and Good News Translation.

Instead of repeating the words David my father, which are in the Hebrew, Good News Translation substitutes them with the pronoun “him” for reasons of English style.

Regarding the idiom it was in your heart, see the comments on verse 17. Good News Translation has dropped the repetition of this expression for reasons of English style.

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on 1-2 Kings, Volume 1. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here .