A condition for God hearing us in prayer, is that we ask according to His will (1 Peter 4:19; Galatians 1:4; Ephesians 1:5, 11). If we ask according to His will, we can always be confident, not only that He hears us, but that we will be granted what we ask for. We were told in chapter 3:22 that we can have confidence that God will hear and answer our prayer when our life is pleasing to Him.
We may also intercede on behalf of a brother who is sinning, and God will give him life, provided it is not a sin leading to death, "death" here meaning physical death. It is not concerned with spiritual death because the child of God has eternal life. It is certainly not the "unpardonable sin" to which the Lord Jesus referred, which is committed by unbelievers against the Holy Spirit and leads to eternal punishment. The sin mentioned here is committed by God's children, and causes sickness and death. The Lord doesn't discipline the Devil's children, but only His own.
There were crimes then and now which bear the death penalty according to the law. This could be one of the meanings of sin leading to death. However, some believers are withdrawn from service and called home by their heavenly Father, prematurely as we might think, because of a sin whereby they are disgracing Him or His people.
We have examples in Scripture, such as Moses and Aaron "Then the LORD spoke to Moses and Aaron, 'Because you did not believe Me, to hallow Me in the eyes of the children of Israel, therefore you shall not bring this assembly into the land which I have given them.'" (Numbers 20:12). Moses pleaded to be allowed to go in and the LORD said to him "Enough of that! Speak no more to Me of this matter" (Deuteronomy 3:26). Both Moses and Aaron had committed a sin leading unto physical death.
In the New Testament we have the example of Ananias and Sapphira, who were guilty of lying to the Holy Spirit (Acts 5:1-11). They were willing to live a lie. Because of that, God removed them from this earthly scene.
There is also the case of some of the early believers in Corinth who had actually been getting drunk at the Lord's Supper, and were missing the meaning of it altogether. Because of this many were weak and sickly among them, and many had died because of their sin (1 Corinthians 11:30).
The nature of the sin can vary:
having lost their tempers, Moses and Aaron disobeyed God's command and so destroyed a type of the Lord Jesus.
in their ambition to be highly regarded, Ananias and Sapphira were lying and were prepared to live like hypocrites.
selfishness and drunkenness caused believers at Corinth to make a mock of the Lord's Table.
So a sin unto death can be different for each one of us. In the above cases, we find disobedience to God, lying to God's people and utter disrespect of the body of Christ (the church). Every believer is capable of committing a sin unto death, but this does not necessarily mean that every believer who dies early in life has committed a sin unto death.
Most sins don't lead to death: all believers who are alive today have sinned but we haven't sinned a sin unto death. We did something that was wrong, it was unrighteousness, but God didn't take us home because of it. If He were taking home every believer who sinned, there would be none left to witness to the unsaved. We must show our love for one another by praying for those of us who fall into sin, such as to upset our fellowship with God. It leads to backsliding (James 5:19-20), immorality (1 Corinthians 5:5) and disregard for the Lord's body, the church (1 Corinthians 11:30). If one such is turned back from the error of his way, he will be saved from physical death, and a multitude of sins are forgiven him (James 5:20).
We are born again, and have been given a new godly nature which will never sin, but has a desire for God and for the things of God. Our old nature is liable to sin and it must be put to death (Romans 8:13, Colossians 3:5); it is that old nature which causes us to sin. Sin is all over in this world, but we are saved day by day from its power if we are vigilant and keep ourselves from falling into it.
That wicked one, our spiritual enemy, Satan, may tempt us, as he tempted the Son of God after he spent forty days without food in the desert, but he cannot touch any son of God. For example, no believer can ever be demon-possessed because "greater is he that is in you, than he that is in the world" (1 John 4:4). We may be oppressed by evil surrounding us, but a demon is not able to enter where the Holy Spirit is dwelling.
We know that we are of God, and when we look around us we cannot but agree that we are living in a world that is under the sway of the wicked one. In other words, we might say that the devil has the whole world around us asleep. The devil keeps saying to us, "Sh-h-h. Hush! You're waking people up, and we don't want to do that! They are very comfortable. Many people in churches are dead in trespasses and sins, and we don't want to wake them up. Let's leave them alone." The devil is concerned when people are awakened.
The true Christian faith is not a religion: it is a person, and that person is the Son of God, Jesus Christ. He came to wake us up and to give us an understanding, so that we may know Him Who is true - the true God, the Maker of the universe. We, who believe in the Lord Jesus, are in fellowship with God and His son Jesus Christ. And this fellowship is eternal life. That fellowship which was broken when Adam, the first of the human race, sinned and thereby died, is restored by our faith in Christ so that now we live. This fellowship will never be broken again, and that is eternal life.
Consequently, we must prevent anything to stand between Christ and ourselves. Any such thing is an "idol": created things, symbols, things of the world which occupy our mind and our attention in place of Christ Himself.
We see pictures of people in other lands, and even in our own, going to heathen temples and worshipping there and we feel sorry for them in the darkness of their idolatry. And we also see it in supposedly Christian places of worship, where both priests, congregations and individuals kneel down before pictures or sculptures, become devotees of "saints", and attribute blessings and miracles to these inanimate objects.
Covetousness also is idolatry (Colossians 3:5): it means a burning and never satisfied ambition to own or attain something above what has been given through faith in Christ. It is striving to always get more money, power, influence, comforts, luxury, job satisfaction. It is the greatest idol of all in the world today, and the root of most of the problems (1 Timothy 6:10). Yet a great many believers succumb to the temptation of worshipping it.
Our bodies are the tabernacle of the Holy Spirit, and they are to be used for God. Money, power, influence, comforts can be used for the glory of God, but Christ must come first, and the things which are above - all others will be added to us. "For the love of money is a root of all kinds of evil, for which some have strayed from the faith in their greediness, and pierced themselves through with many sorrows" (1 Timothy 6:10). The root of all evil is the love of money (covetousness), not money in itself. There are many men, even Christians, who are working on that second million, and they don't need it. It is because they worship an idol. If we are in Christ, He will come first and we will seek those things which are above.
Amen: this is truth, and this is sure.
14 And this is the confidence which we have in him, that if we ask anything according to his will he hears us.
15 And if we know that he hears us in whatever we ask, we know that we have obtained the requests made of him.
16 If any one sees his brother committing what is not a mortal sin, he will ask, and God will give him life for those whose sin is not mortal. There is sin which is mortal; I do not say that one is to pray for that.
17 All wrongdoing is sin, but there is sin which is not mortal.
18 We know that any one born of God does not sin, but He who was born of God keeps him, and the evil one does not touch him.
19 We know that we are of God, and the whole world is in the power of the evil one.
20 And we know that the Son of God has come and has given us understanding, to know him who is true; and we are in him who is true, in his Son Jesus Christ. This is the true God and eternal life.
21 Little children, keep yourselves from idols.