Prayer is a foundation stone benefit associated with the Christian life. We can actually communicate messages to God while He is not visibly manifested and we can do so with the confidence that he hears those prayers and answers them. However, we do have some conditions for having this confidence and one of those is that our prayers are according to the will of God. In our passage the will of God is that we make requests on behalf of a believer who commits sin not leading to death.
"Confidence" described here primarily relates to the Christian's confidence in asking things of God. So we can have confidence in regard to answered prayer before God.
The qualification the author places on this promise of answered prayer for the believer is that the request must be in accordance with God's will. This is just what the author said earlier in 1 John 3:21-22, in a context where "confidence" before God was the subject, as it is here. In 3:22 the author stated that the reason believers receive from God whatever they ask is "because we keep his commandments and do the things that are pleasing to him." To "keep God's commandments" in 1 John 3:22 is to do God's will, and this is why the believer may confidently expect to have his or her prayers answered.
Doing God's will in the context of 5:14 may be more narrowly defined as praying for the person who sins but does not commit the "sin resulting in death" (5:16a) while not praying for the person who does commit the "sin resulting in death" (5:16b). So doing God's will is the kind of praying about sin not unto death and the sin unto death. These are the prayers we can be certain of God answering. In ones sense this encompasses all of our praying. When it is within the will of God then you are assured of an answer. Specifically, within the context it is in regards to God's will concerning sin in the believer's life, which follows. God has a specific will about sin. We may have our own will concerning sin but that does not figure in the equation.
Twice John says 'we know'—that he hears us, and that we have answers. Here it is not knowledge in the sense of information or facts, or knowledge from observation—this kind of knowledge is knowing in the sense of information is security. Instead it is knowing in the sense of conviction---I know God loves me. In this case we can suppose that a Christian has the right to ask God for help in keeping His commandments for himself and other believers.
The entire passage is governed by the concept of making requests of God. We see this in v 14 'ask'; v 15 'ask' and 'requests' and 'asked'; v 16 'ask' and 'request'. So a basic component or praying is 'asking' things of God—specific things as in this context—but encompassing all kinds of things in life. The biggest single challenge we all face about prayer is praying! We just do not take up praying as a significant component of our Christian living. Yet, scripture teaches us that it must be a significant Christian activity. And a basic aspect of effective prayer is that our requests are according to the 'will of God'!
Sins committed by believers (sins "not resulting in death") may be prayed for and forgiven. The answer to prayer is specifically about a brother committing a sin not leading to death. There are sins we can recover from and sins we cannot recover from in this life. 1:10 are sins we can recover from since they are ones we confess. We agree with god about what he says it is. Other sin we cannot recover from. Sin is missing the moral mark of God, and anything contrary to the character of God. John does not tell us what, if any, specific sin he has in mind. But it would be a sin not confessed. Most of our sins are not sins so serious that God judges that sin with swift physical death (sin leading to death). For these, a believer ought to pray knowing that any sin—if continued long enough or potentially harmful enough—is a threat to a fellow Christian's life (James 5:19-10; Acts 5:1-11; 1 Cor 5:5; 11:29-30; cf. 1 Tim 1:20; Jas 5:15; Rev 2:23). Thus a restoration of a brother may secure a prolonging of his physical life and the further opportunity to lay up treasure and rewards in heaven which a shortened life threatens. All sin does lead to death ultimately but may not include punishment by death prematurely. This sin not leading and leading to death could also simply refer to sin we can recover from in this life and sin we cannot recover from in this life most likely because we refuse to confess it as sin and so continue to live with the consequences of not being forgiven by God and the temporal outcome of that sin.
Sin that leads to death or is punished by death, flagrant sins, is not something we must necessarily be knowledgeable enough about to have to make a request for v 16b as long as we can recognize many which are not. We are commanded to pray regarding sins, which are not punishable by death or can be recovered from. We have the freedom to pray for any sin in any believer's life and even if it a seriously flagrant one, we can submit those prayers to the will of God. So we can pray with confidence when we pray about another Christian brothers sin!
Here, having implied that sins committed by believers (sins "not resulting in death") may be prayed for and forgiven, we cannot have the impression that such sin is insignificant, because we should never downplay the significance of sin in the Christian's life. Therefore he reminds his readers that all unrighteousness is sin. When we do pray for this sin we are demonstrating our love for our brother. Loving our brother includes praying about his or her sin because such praying is in the will of God. We are motivated by the fact that sin is offensive to God and will have consequences. It is never better to sin.
Even though we are believers, we are weak and vulnerable to sin because of our flesh and old nature. So it will always be a struggle we accept but in the will and power of God we pursue victory. Yet sin does trip us up and for that we must pray when it is happening. Sin by its very nature is unrighteousness and incompatible to the Christian life.
(1) Sin is always more serious with God than it is with us.
(2) We must have a ministry of intercessory prayer for one another's sin.
(3) Sin is the issue and so much so because it delivers destructive consequences even for believers. Those consequences include punishment by physical death, unforgiving sin accountable before God, loss of reward—all of these significant form the vantage point of eternity.