Answered by Randy Alcorn
Suicide is the unjustified killing of a human being, and is therefore forbidden in the commandments not to murder. Scripture says very little directly about suicide. However, it says much about God's character and we can certainly trust in His love, fairness and judgment.
If a man truly knows Christ, then regardless of what he does, he cannot be snatched out of his Father's hand (John 10:27, 28). Ephesians 1:13 and 2 Cor. 1:22 speak of believers being sealed in Him. Only God knew his heart if he truly was a believer. If he was, then it seems like what would have been changed by the suicide would be his fellowship with the Lord, not his salvation.
God has already forgiven our sins, past, present and future when we trust in Him as our Savior and Lord. But he wants us to confess our sins to restore fellowship with Him, as 1 John 1:9 says. A person who commits suicide, if it is instantaneous, wouldn't have opportunity to confess that sin before dying. Presumably that would mean having to confess and repent upon meeting God after death. Christ died for sins of suicide, so suicide is forgivable—but it is also tragic, unnecessary and cruel and debilitating for loved ones left behind.
In my book Heaven, I include this:
A Word to the Depressed
The fact that Heaven will be wonderful shouldn't tempt us to take shortcuts to get there. If you're depressed, you may imagine your life has no purpose—but you couldn't be more wrong.
As long as God keeps you here on Earth, it's exactly where he wants you. He's preparing you for another world. He knows precisely what he's doing. Through your suffering, difficulty, and depression, he's expanding your capacity for eternal joy. Our lives on Earth are a training camp to ready us for Heaven.
I know depression can be debilitating. Many godly people have experienced it. But if you are considering taking your own life, recognize this as the devil's temptation. Jesus said that Satan is a liar and a murderer (John 8:44). He tells lies because he wants to destroy you (1Peter 5:8). Don't listen to the liar. Listen to Jesus, the truth teller (John 8:32; 14:6). Don't make a terrible ending to your life's story—finish your God-given course on Earth. When he's done—not before—he'll take you home in his own time and way. Meanwhile, God has a purpose for you here on Earth. Don't desert your post. (And by all means, go to a Christ-centered, Bible-believing church, and get help to find a wise Christian counselor.)
If you don't know Jesus, confess your sins and embrace his death and resurrection on your behalf. If you do know him, make your daily decisions in light of your destiny. Ask yourself what you can do today, next week, next year, or decades from now to write the best ending to this volume of your life's story—a story that will continue gloriously in the new universe.
By God's grace, use the time you have left on the present Earth to store up for yourself treasures on the New Earth, to be laid at Christ's feet for his glory (Revelation 4:10). Then look forward to meeting in Heaven Jesus himself, as well as those touched by your Christ-exalting choices.
