12 So he sent for him and had him brought in. He was glowing with health and had a fine appearance and handsome features. Then the Lord said, "Rise and anoint him; this is the one." 13 So Samuel took the horn of oil and anointed him in the presence of his brothers, and from that day on the Spirit of the Lord came powerfully upon David. Samuel then went to Ramah.

Matthew Henry's Commentary on 1 Samuel 16:12-13

Commentary on 1 Samuel 16:6-13

(Read 1 Samuel 16:6-13)

It was strange that Samuel, who had been so disappointed in Saul, whose countenance and stature recommended him, should judge of another man by that rule. We can tell how men look, but God can tell what they are. He judges of men by the heart. We often form a mistaken judgment of characters; but the Lord values only the faith, fear, and love, which are planted in the heart, beyond human discernment. And God does not favour our children according to our fond partiality, but often most honours and blesses those who have been least regarded. David at length was pitched upon. He was the youngest of the sons of Jesse; his name signifies Beloved; he was a type of God's beloved Son. It should seem, David was least set by of all the sons of Jesse. But the Spirit of the Lord came upon David from that day forward. His anointing was not an empty ceremony, a Divine power went with that instituted sign; he found himself advanced in wisdom and courage, with all the qualifications of a prince, though not advanced in his outward circumstances. This would satisfy him that his election was of God. The best evidence of our being predestinated to the kingdom of glory, is, our being sealed with the Spirit of promise, and experience of a work of grace in our hearts.