QUESTION: If God has mercy on us and forgives us, why are there verses in the Bible that say we will be condemned if we commit a certain sin? Does it mean those who are not saved will be condemned? Or is it referring to everyone in general?
ANSWER: Thanks for the good questions. You don't mention any specific examples of verses that apply, so let me treat the questions by dealing with some broader truths.
Your first question seems to contain a logical contradiction. If we are forgiven, how can we also be condemned for sins that have been forgiven?
Let's back up a few steps, to lay a foundation. God is a God of righteousness, holiness and justice. "The Lord our God is holy [utterly separate and set apart from any sin or corruption]" (Ps. 99:9; I Jn. 1:5). And, as a holy God, He is "angry with the wicked every day" (Ps. 7:11).
Any failure to trust in and obey God is sin (Rom. 14:23; I Jn. 5:17).
And all sin is bad, and deserving of eternal condemnation. "The wages of
sin is death [eternal death, a separation from God forever]" (Rom.
6:23a; cf. Rev. 21:8). The unbeliever "shall not see life, but the wrath
of God abides on him" (Jn. 3:36).
As to human beings (apart from the incarnate Son of God, who was "without sin," Heb. 4:15) "all have sinned and fall short of the glory of God" (Rom. 3:23). "There is none righteous, no, not one" (vs. 10). And in that condition, all are justly condemned. From the very beginning, the Lord has pledged that He must and will punish sin (Gen. 2:17).
On the other hand, there is ample evidence, in the Bible, of God's saving grace, His unmerited favour. No one is saved because he's earned it or deserves it (Eph. 2:8-9). Instead God, in love, sent His Son to take sin's punishment in our place. He "suffered once for sins, the just for the unjust" (I Pet. 3:18). "Christ died for our sins according to the Scriptures" (I Cor. 15:3). He died for all the sins of all, for all time. His sacrifice fully satisfied God's justice for the sins of "the whole world" (I Jn. 2:2; cf. Isa. 53:6).
But not all will be saved, only those who have personally claimed Christ's payment for themselves by faith (Jn. 3:18; Acts 16:30-31). The offer of full forgiveness and cleansing is made to any who will put their faith in Christ as Saviour. All who trust in Him as their Saviour are forgiven, and given the gift of eternal life (Jn. 3:16). "The gift of God is eternal life in Christ Jesus our Lord" (Rom. 6:23b). Those who trust in Christ become children of God (Jn. 1:12-13).
Now we get to the issue you raised, and the answer is there are two kinds of forgiveness, or two aspects of God's forgiveness. They are what we might call judicial forgiveness, pertaining to sinners in the court of God (Heb. 9:27), and parental forgiveness, pertaining to saints in the household of God. Sin is still sin, but the saint (the Christian) has a completely different standing before God than the sinner (the unsaved).
The unsaved are in need of judicial forgiveness. They are destined to face God, the Judge, with sins on their record. Both because of their sinful, fallen nature, and because of the expression of that nature in acts of sins, they will be eternally lost. But when they trust in Christ they are delivered from all condemnation for sins past, present, and future (Col. 2:14).
The position of the children of God is quite different. The eternal condemnation for all our sins has been dealt with fully and forever at the cross. Our names are written in the Lamb's book of life, and that makes all the difference (Rev. 20:15). There can be no condemnation for those who are in Christ (Jn. 5:24; Rom. 8:1), since His perfect righteousness has been credited to our account (II Cor. 5:21).
Christians do stumble into sin from time to time, but it has ceased to be the pattern of our lives. The Christian no longer faces God as a Judge, but as his heavenly Father. When we sin, Christ is our "Advocate with the Father" (I Jn. 2:1). We are to confess it before God and receive His complete forgiveness (I Jn. 1:9).
Nothing can ever separate the child of God from His love (Rom. 8:33-39). As children of God, we don't lose our salvation when we sin. But fellowship with God is broken. There is a loss of joy, and of power in service, and certainly a loss of eternal rewards. But not a loss of sonship.
Even so, it is important to deal with sin in our lives. As Christians, we are indwelt be the Spirit of God (Rom. 8:25) and desire to please our heavenly Father, serving Him effectively (cf. Ps. 51:12-13).