Context: this passage regards the Lord's command to the priest Samuel. He told Samuel to go to Bethlehem, to visit the family of Jesse, and that one of his sons would be the future king. Jesse trotted out seven sons, one after another, but the Lord told Samuel to ignore all of them. Samuel asked Jesse if there was anyone else, and Jesse called his youngest, David. The following occured when Samuel decided that the first son, Eliab, was the obvious choice.
But the Lord said unto Samuel, Look not on his countenance, or on the height of his stature; because I have refused him: for the Lord seeth not as man seeth; for man looketh on the outward appearance, but the Lord looketh on the heart.
1 Samuel 16:7 KJV
But God told Samuel, “Looks aren’t everything. Don’t be impressed with his looks and stature. I’ve already eliminated him. God judges persons differently than humans do. Men and women look at the face; God looks into the heart.”
1 Samuel 16:7 MSG