1Sam:18:8: And Saul was very wroth, and the saying displeased him; and he said, They have ascribed unto David ten thousands, and to me they have ascribed but thousands: and what can he have more but the kingdom?
1Sam:18:9: And Saul eyed David from that day and forward.
Saul feared David had become more popular than him. He was already paranoid that someone would take the kingdom from him as the Lord, through the prophet Samuel had foretold.
Because king Saul was jealous and wanted to kill him.
King Saul was very jelous of David because god was with him and also he was Jonathans , Sauls sons best friend. He was also jealous because God said to Saul that the will be another King to take over him.He then figured that it will be David so he asked for him to be dead.
King David was in exile from Saul for approximately seven years. After Saul became increasingly jealous of David's popularity and success, David fled to escape Saul's attempts on his life. This period of exile included time spent in various locations, such as the wilderness of Judah and the city of Ziklag, until Saul's death, which ultimately allowed David to ascend to the throne.
King Saul became jealous of David due to David's rising popularity and success, particularly after he defeated Goliath and the women sang praises of David, stating that he had slain "tens of thousands" while Saul had only slain "thousands." This jealousy intensified as David continued to gain favor with the people and was seen as a threat to Saul's throne. Saul's jealousy ultimately led to a series of attempts to kill David.
David won Michal's hand in marriage when he fulfilled King Saul's challenge to kill 100 Philistines all by himself. Michal was King Saul's daughter. King Saul hated David because he was jealous of him and was hoping that David would be killed trying to fulfill the King's request. David killed twice the number of Philistines required of the King and so Michal was given to David to be his wife. Ref: (I Samuel 18:26-30).
Saul, the first Israelite king, was followed by King David. See also:Choosing the first kingMore about King SaulThe transition of the throne from Saul to David
There was no King Paul. But there was Paul the Apostle. His name was also Saul. Now there was a Jewish King named Saul, perhaps that's whom you mean. He was the King that ruled over Israel for 40 years, immediately preceeding the reign of King David. The last years of his life he lost God's blessing on his reign, God then picked David to be the next King. Saul was jealous of how God was with David, and so sought to have him killed on numerous occasions. Saul and his son Jonathan (who was very close friends with David before David was king) were both killed in a battle that saw King Saul's forces defeated by the Phillistines.
The difference between King David and saul was that david listened to god and even repented again and again. But it was not so with Saul.
David was Saul's immediate successor.
King Saul was jealous of David, but Saul offered his daughter, Michal to David as a wife. David said he was too poor to give a dowry to Saul for his daughter, but Saul said he wanted no dowry, but wanted David to avenge him (Saul) upon the Philistines by bringing 100 foreskins of the enemy back to him. But Saul's motive was not what he said, but rather he wanted David to engage in battle with the Philistines in hopes that David would be killed.
King Saul noticed that David was increasing in popularity as war-hero and therefore jeopardized the right of his lineage to rule. Only by killing David could he ensure that his son Jonathan would succeed him as King of Israel. Saul's fears proved correct when David inherited Saul's throne upon the latter's death in the Battle of Mt. Gilboa. (It is worth noting that Jonathan and all of Saul's other sons also died in that battle.) It should be noted that Saul is seen not as a wicked man, but as a righteous man (Talmud, Moed Katan 16b) who erred.
It was the sword and the crown of King Saul that Amalekite took to David after King Saul's death.