I Samuel 16

I Samuel 16:7:
But the Lord said to Samuel, "Do not look at his appearance or at the height of his stature, because I have refused him. For the Lord does not see as man sees; for man looks at the outward appearance, but the Lord looks at the heart."

“And he who searches our hearts knows the mind of the Spirit, because the Spirit intercedes for God’s people in accordance with the will of God.”
(Romans 8:27)

““I knew you before I formed you in your mother’s womb.”
(Jeremiah 1:5)

"As for you, my son Solomon, know the God of your father, and serve Him with a whole heart and a willing mind; for the LORD searches all hearts, and understands every intent of the thoughts If you seek Him, He will let you find Him; but if you forsake Him, He will reject you forever.”
(1 Chronicles 28:9)

In the passage in 1 Samuel 16, God contrasted the outward appearance against the inner workings of the heart, declaring that the heart was more important than outward looks. This sentiment is echoed in Isaiah 29:13 when God points out about the Israelites, "This people draw near with their mouth and honor me with their lips, while their hearts are far from me." Despite the Israelites' outward actions and spoken words, God knew their hearts were not in line with their appearances. Jesus also said the same of the Pharisees: "So you also outwardly appear righteous to others, but within you are full of hypocrisy and lawlessness" (Matthew 23:28). With these two examples, God makes it clear that He is more concerned with the inner hearts of people rather than with their outwardly conforming to religious standards—God looks at the heart and is not fooled by our facades. Jesus said that the most important commandment was, "You shall love the Lord your God with all your heart and with all your soul and with all your mind" (Matthew 22:37). God desires our deep love, loyal devotion, and full attention more than our outward obedience
--Compelling Truth

I Samuel 16:14:
But the Spirit of the Lord departed from Saul, and a distressing spirit from the Lord troubled him.

"This is a difficult passage for two reasons. First, it seems to imply that a person can lose the Holy Spirit by an act of disobedience. But it must be understood that the presence of the Holy Spirit in the Old Testament was selective and temporary. The Spirit involved with Saul was probably the same Spirit involved with David in verse 13: a special equipping of the Spirit for ruling as God's anointed king. This unique equipping is not the same as the personal relationship in the Spirit that we enjoy with God as His children today." --Neil T. Andersom (The Bondage Breaker)