Psalm 56:9-11 KJV
When I cry unto thee , then shall mine enemies turn back: this I know; for God is for me.
 In God will I praise his word: in the Lord will I praise his word.
 In God have I put my trust: I will not be afraid what man can do unto me.
Like any other King, David had many adversaries. Be it internally or externally, people would always find reason not to be on his side, or simply hate him. It comes to everyone in an enviable position.
This was evident throughout his life, especially when he became king, even though he was anointed. And one thing we know for sure is that David trusted God fully. His Trust in God for protection against such close and far ‘enemies’ was so tangible that they all saw it.
In fact, ALL those who found themselves around David knew that if he cried out to God on any day, God would lift His eyes against them and all others in any such plot, and that would spell disaster for them. (see v9)
It is very important for every believer to make his close associates KNOW who’s got his back. Not everyone should be able to mess you up, no not at all. Establish that and make it work for and on your behalf.
Have a blessed day.