He claims the Lord as his by inheritance. Now it is his turn to call for obedience. He recognizes God's counsel and instruction. The good things of life are in God's hands.
Come take of his bounty and the rejoice of his presence.
Saul was the first king of Israel, but he was disobedient and presumptuous, and God told Samuel he would be rejected. Samuel tried to claim forgiveness and repentance for Saul, but when he continued in his arrogance, Samuel anointed David to succeed him.(1 Samuel 16) Saul was still King, and David was still herding his father's sheep. The Spirit of the Lord had departed from Saul. An evil spirit tormented Saul, so they sought for a musician to play a lyre to calm him when this happened. Someone knew about David's skill in music and they sought him out.
David impressed Saul. He was helpful with the vexations from the evil spirit and he was good company. He brought with him, wine, bread and meat. Saul received relief and David went home.
Chapter 17 of 1 Samuel tells the story of David and Goliath, and Saul is reminded of the brave and talented young man.
David was given command of troops and was successful in his campaigns. (1 Samuel 18) Saul grows jealous of David's success. Saul promised David his daughter Michal marriage. Both Michal and Jonathan warned David and helped him escape Saul's anger. David never tried to kill Saul though he had opportunities.
David ran from the attack of Saul for years recounted in the rest of 1 Samuel. The death of Saul is recounted in both 1 Samuel 31 and 2 Samuel 1 giving different details.
Saul and his three sons were found and the Philistines claimed victory. David weeps for his friend Jonathan and lamented for Saul and his sons.
Read Psalms 18 and look for indications of his loyalty to Saul and his praise for God.
Psalms 18:2 contains many words that reflect David's mindset: God delivered him using a fortress, shield, and stronghold. He recalls the years of threat from Saul in terms of the a struggle for life. Psalms 18:3-5 detail the constant fear he experienced from Saul's men.
There are hints in the Psalm of natural events that plagued David during the time in the wilderness when he was hiding and running from Saul. He speaks of thunder and lightning. I envision a storm that put his life at risk. (Vs. 13&14)
He says God drew him out of "deep waters" in vs. 16. I did not find a place in the test of 1 Samuel that can traced to these events, but in the years he spent as a fugitive, surely these are possible.
Read Psalms 18 for a richer understanding of David and his worship of God.