How did one of the servants of Saul know that the Lord was with David in 1 Samuel 16:18?
I think the best indication of what the young servant of Saul meant when he said "the LORD is with him" is found in the rest of the quote: "Behold, I have seen a son of Jesse the Bethlehemite, who is skillful in playing, a man of valor, a man of war, prudent in speech, and a man of good presence, and the Lord is with him.”
This servant saw several distinguishing characteristics in David:
- He was a skillful musician.
- He was brave, a man of valor.
- He was skilled with weapons, a man of war.
- He was prudent, or wise, in his speech.
- He was "a man of good presence," someone who has charisma and obvious leadership potential.
The servant thus concluded that a man this gifted must be blessed by the Lord, and so he wrapped up his assessment by saying "the Lord is with him." In other words, I don't think he was claiming any prophetic insight into David's destiny, but making a theologically informed assessment of David's character and abilities as evidence of being blessed by God.