What should a Christian do?

 "I, the Lord, search to the heart, I probe the loins, to give each man what his conduct and his actions deserve."

This quotation echoes Jeremiah 17:10 and Revelation 2:23: the Lord searches the heart and inner motives (“reins/loins”) and repays according to our ways. 

In light of this, a Christian should:

• Invite God’s searching and submit to it: “Search me, O God…lead me in the way everlasting,” approaching Him with humility and teachability (Jer 17:10; Ps 139:23–24) [2].
• Repent quickly and confess specifically, trusting God to cleanse and restore fellowship (Acts 3:19; Prov 28:13; 1 John 1:9) [2].
• Depend on Christ’s grace for a new heart and an obedient walk, not self-reliance (Ezek 36:26–27; Titus 3:5–7; Eph 2:8–10) [2].
• Align conduct with God’s Word—be a doer, not a hearer only; obey Jesus’ commands in love (James 1:22–25; John 14:15; Mic 6:8) [2].
• Guard the inner life (motives, desires, thoughts), since God “tries the reins,” and let His Word and Spirit purify them (Prov 4:23; Heb 4:12–13; 1 Cor 4:5; Gal 5:16–25) [2].
• Live with the judgment seat and reward in view, sowing to the Spirit and persevering in well-doing (2 Cor 5:10; Rom 2:6–11; Gal 6:7–9; Rev 22:12) [2].
• Practice ongoing self-examination with prayer, Scripture, fellowship, and the Lord’s Table, receiving His loving discipline (1 Cor 11:28–32; Heb 12:5–11) [2].
• Make restitution and seek reconciliation where you have wronged others; pursue peace and practical righteousness (Matt 5:23–24; Luke 19:8–9; Rom 12:18) [2].
• Abound in good works that flow from faith—a life of service, mercy, and holiness (Eph 2:10; Titus 2:11–14; Matt 25:31–46; 1 Thess 4:3–7) [2].

In short: welcome God’s search, repent where He convicts, trust Christ to cleanse and empower, and walk in obedient, Spirit-led integrity—knowing He sees the heart and will render according to our deeds (Jer 17:10; Rev 2:23) [2].

Sources

1 Biblical Theology by Geerhardus Vos

2 The Dake Annotated Reference Bible, King James Version, Large Print Edition, 1999, Containing Old and New Testaments, by Finis Jennings Dake

text, Old Testament, i-1598 text, New Testament, 1-561 text, complete concordance and cyclopedic index, 1-163. text, Plan of the Ages, 0-24...

3 The New Strong's Expanded Exhaustive Concordance of the Bible: Every Word of the Bible Indexed, Red Letter Edition The New Strong's Expanded Exhaustive Concordance of the Bible: Every Word of the Bible Indexed, Red Letter Edition