Jesus replied: ” ‘Love the Lord your God with all your heart and with all your soul and with all your mind.’ Matthew 22:37

Above all else, guard your heart, for it is the wellspring of life. Proverbs 4:23

Guard your heart from self-deception

“The heart is deceitful above all things and beyond cure. Who can understand it? I the LORD search the heart and examine the mind, to reward a man according to his conduct, according to what his deeds deserve.” Jeremiah 17:9-10

If we claim to be without sin, we deceive ourselves and the truth is not in us. 1 John 1:8

When they went across the lake, the disciples forgot to take bread. “Be careful,” Jesus said to them. “Be on your guard against the yeast of the Pharisees and Sadducees.” Matthew 16:5-6

To some who were confident of their own righteousness and looked down on everybody else, Jesus told this parable: “Two men went up to the temple to pray, one a Pharisee and the other a tax collector. The Pharisee stood up and prayed about himself: ‘God, I thank you that I am not like other men–robbers, evildoers, adulterers–or even like this tax collector. I fast twice a week and give a tenth of all I get.’ “But the tax collector stood at a distance. He would not even look up to heaven, but beat his breast and said, ‘God, have mercy on me, a sinner.’ “I tell you that this man, rather than the other, went home justified before God. For everyone who exalts himself will be humbled, and he who humbles himself will be exalted.” Luke 18:9-14

Guard your heart from hypocrisy

“You hypocrites! Isaiah was right when he prophesied about you. ‘These people honor me with their lips, but their hearts are far from me. They worship me in vain; their teachings are but rules taught by men.'” Matthew 15:7-9

Who may ascend the hill of the LORD? Who may stand in his holy place? He who has clean hands and a pure heart, who does not lift up his soul to an idol or swear by what is false.
Psalm 24:3-4

God is spirit, and his worshipers must worship in spirit and in truth.” John 4:24

Do not merely listen to the word, and so deceive yourselves. Do what it says. Anyone who listens to the word but does not do what it says is like a man who looks at his face in a mirror and, after looking at himself, goes away and immediately forgets what he looks like. But the man who looks intently into the perfect law that gives freedom, and continues to do this, not forgetting what he has heard, but doing it–he will be blessed in what he does. James 1:22-25

Guard your heart from apathy

I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! So, because you are lukewarm–neither hot nor cold–I am about to spit you out of my mouth. Revelation 3:15-16

Surely you desire truth in the inner parts; you teach me wisdom in the inmost place. Cleanse me with hyssop, and I will be clean; wash me, and I will be whiter than snow. Let me hear joy and gladness; let the bones you have crushed rejoice. Hide your face from my sins and blot out all my iniquity. Create in me a pure heart, O God, and renew a steadfast spirit within me. Do not cast me from your presence or take your Holy Spirit from me. Restore to me the joy of your salvation and grant me a willing spirit, to sustain me. Psalm 51:6-12

Love must be sincere. Hate what is evil; cling to what is good. Be devoted to one another in brotherly love. Honor one another above yourselves. Never be lacking in zeal, but keep your spiritual fervor, serving the Lord. Be joyful in hope, patient in affliction, faithful in prayer. Share with God’s people who are in need. Practice hospitality. Romans 12:9-13

Every day they continued to meet together in the temple courts. They broke bread in their homes and ate together with glad and sincere hearts, Acts 2:46