Saul spoke to David before the fight with Goliath, entrusting the future of the entire nation to him and giving his own armour, without knowing enough about David.

"“All right,” Saul answered. “Go, and the LORD be with you.” He gave his own armour to David for him to wear: a bronze helmet, which he put on David's head, and a coat of armour. David strapped Saul's sword over the armour and tried to walk, but he couldn't, because he wasn't used to wearing them. “I can't fight with all this,” he said to Saul. “I'm not used to it.” So he took it all off.

...

When Saul saw David going out to fight Goliath, he asked Abner, the commander of his army, “Abner, whose son is he?”

“I have no idea, Your Majesty,” Abner answered.

“Then go and find out,” Saul ordered.

So when David returned to camp after killing Goliath, Abner took him to Saul. David was still carrying Goliath's head. Saul asked him, “Young man, whose son are you?”

“I am the son of your servant Jesse from Bethlehem,” David answered."

(1 Samuel 17.37-39,55-58 GNB)

Obviously Saul was desperate for somebody who was brave enough to face Goliath. Had it not been for God's plan, Saul's action could turn out bad for the nation.

Some people are also like Saul. Trusting and following certain influencers and leaders without truly knowing. But many of them would not turn out so good as David.

Lord,
please help me be wise in knowing and trusting people