Rend your heart and not your garments. Return to the Lord your God, for he is gracious and compassionate, slow to anger and abounding in love, and he relents from sending calamity (Joel 2:13).
Just about anything can be feigned: love, obedience, gratitude, or repentance.
Men may be fooled by pretentious acts, God is not. Thus, "Rend your hearts..."
For the Jew, tearing one's garment expresses grief, but like anything else, this could be contrived (Matt. 26:65). An outward change of behavior is desirable, but is not the final test: "...judge nothing before the appointed time; wait until the Lord comes. He will bring to light what is hidden in darkness and will expose the motives of men’s hearts. At that time each will receive his praise from God" (1 Cor. 4:5).
You rightly believe that "the one who does the will of the Father will enter the Kingdom of Heaven" (Matt. 7:21). Rightly do you believe that we must "be doers of the Word, not merely hearers who delude themselves" (Jas. 1:22).
Serving God is not strictly a matter of performance–"if I have a faith that can move mountains, but do not have love, I am nothing" (1 Cor. 13:2).
Faith must work through love (Gal. 5:6).
God is equally concerned with WHY we do what we do. He seeks a changed heart–one wholly dedicated to Him. He seeks hearts broken over sin–"a broken and a contrite heart, O God, You will not despise" (Ps. 51:17). That is the only kind of heart that will return to the Lord. We fall short of His glory because of our sin. Sadly, one may pretend sorrow, feign repentance, and pray sanctimoniously for all to see.
One can do all these things without ever rending his heart. This should be a cause for great concern. Sin is what separates you from God and every blessing found in Him. Though He knows the precise number of your sins, He desires to take them away in Christ.
If You, Lord, should mark iniquities, O Lord, who could stand? But there is forgiveness with You, that You may be feared (Ps. 130:3-4).
You will face God and answer for your choices, as I will for mine.
Yet God is not eager to mark sin, nor is He eager to condemn.
He sees us more clearly than we could ever see ourselves, and while God hates sin, He is not vindictively, anxiously looking forward to punishing people–"'Do I have any pleasure in the death of the wicked,' declares the Lord GOD, 'rather than that he should turn from his ways and live?'" (Ez. 18:23).
Just the opposite. God grieves over sin in peoples' lives–"For the brokenness of the daughter of my people I am broken; I mourn, dismay has taken hold of me" (Jer. 8:21).
Sin should make us angry, not vengeful or malicious. We should be sorry enough to earnestly seek reconciliation and forgiveness.
God is a God of justice who will punish sin, but He is a God of mercy who gives all people a chance to stand before Him forgiven through the blood of Christ.
He is worthy, He is holy, He is to be feared.