Chapter 18

And Jonathan took off the robe that was on him and gave it to David, with his armour, even to his sword and his bow and his belt. (1 Samuel 18:4)

Jonathan was able to perceive the hand of the LORD upon David because he had completely surrendered to the Lord. He was absolutely willing to put David's destiny ahead of his own ambitions in order to honour the choice made by the LORD. 

So the women sang as they danced, and said:
“Saul has slain his thousands,
And David his ten thousands.” (1 Samuel 18:7)

The women in all the cities of Israel sang and danced in honour of David. This was a sure sign of his popularity. However, David was wise enough not to let this popularity cloud his vision and call. 1 Samuel 18:14 says, “And David behaved wisely in all his ways, and the LORD was with him.” In this environment of extreme praise and popularity, David behaved wisely in all his ways.

And it happened on the next day that the distressing spirit from God came upon Saul, and he prophesied inside the house. So David played music with his hand, as at other times; but there was a spear in Saul’s hand. (1 Samuel 18:10)

In this context, the word "prophesied" is not an accurate translation. Saul simply rambled on incoherently like a man who had lost his mind.

David obviously had skilful hands, both in war and in music ministry. The same hands that had previously slain Goliath now played pleasant music to the LORD while ministering to a king who was plagued by a demonic spirit.

Now Michal, Saul’s daughter, loved David. And they told Saul, and the thing pleased him. (1 Samuel 18:20)

It shouldn't surprise us that Michal was attracted to David because of his character, qualities, and fame. But as is evident later in David’s marriage to Michal, she was not really attracted to David’s heart for the LORD.

Then Saul said, “Thus you shall say to David: ‘The king does not desire any dowry but one hundred foreskins of the Philistines, to take vengeance on the king’s enemies.’ ” But Saul thought to make David fall by the hand of the Philistines. (1 Samuel 18:25)

From this, we can see the manipulative heart of Saul. He had gone back on his word to give his daughter to the one who killed Goliath. The request of one hundred foreskins of the Philistines was to put David’s life at stake. Saul wanted him dead.