It appears as if Jesse did not think that his youngest son would be an appropriate candidate for service to the Lord.1 Because he was the youngest and the smallest, he thought it best to leave him tending the sheep so that the older boys could spend time with Samuel. Interestingly, the Lord’s choice of Jesse's youngest is similar to his earlier choice of Jacob (Genesis 25:23) and Ephraim (Genesis 48:8–22).2
11 Then Samuel said to Jesse, “Are all your sons here?” And he said, “There remains yet the youngest, but behold, he is keeping the sheep.” And Samuel said to Jesse, “Send and get him, for we will not sit down till he comes here.”