This doctrine is essential to a proper understanding of many biblical texts. Without this framework, entire blocks of Scripture are literally impossible to understand. However, this begs a crucial question for the introspective reader: how do I know that I am not one of them?
The Bible fortunately anticipates this critical question asked by its readers. The answer that it gives is that of biblical assurance. Assurance is an interesting topic to study throughout the Bible and the New Testament in particular. There are many answers that the Bible gives to fill out this concept of assurance. In fact, the entire letter of 1 John is almost singularly devoted to this doctrine. However, there is a particular aspect or emphasis to assurance that has been simply hammering me in my recent studies. It is found in essence in several pieces, but is distilled in the book of Hebrews:
Hebrews 6:9–10 (ESV) — 9 Though we speak in this way, yet in your case, beloved, we feel sure of better things—things that belong to salvation. 10 For God is not unjust so as to overlook your work and the love that you have shown for his name in serving the saints, as you still do.
Have you ever heard somebody say something to the effect of "I like Jesus, but I just don't like the church." There is a sense in which we can sympathize with their feelings. Oftentimes we recognize that the people that make up the visible church are imperfect and frankly, hypocritical. However, the assurance of salvation that is provided here strikes at the very heart of such thinking. It is precisely because of their devotion to the people of God, the church, that the Christians reading this letter can know that they have salvation.
Getting the order is important here. It is not that serving in God's church is the work that you must do in order to earn your passage into heaven. Rather, salvation comes first and the service and love that flows out of that salvation demonstrates that you have indeed been saved. It follows then that while not everybody who serves in the church and loves the brethren is saved, everyone who is saved will serve in the church and love the brethren.
Again, I must qualify what I am saying at this point. Does everyone who will ever believe have to sign up for ministry opportunities at their church? Does one's lack of participation in church activities indicate that they are damned? Obviously neither of these is unequivocally the case. Membership in God's kingdom is not established by outward actions, but a changed heart. However, we must take seriously the biblical assertion that one way that salvation manifests itself in God's people is through their love for the other people of God. The Bible knows nothing of "lone wolf" Christians. Neither is the concept of those who have a personal relationship with God, but don't spend any time with God's people a plausible one. When someone is saved by the Spirit of God they are adopted into the family of God. Those who are truly adopted into God's family, love God's family and want to spend time with them. Sure the institution of the church may be imperfect at times, but if one would be united to Christ, he must be united to and serve Christ's body as well.
The entire book of first John speaks to this topic as well. John tells us that one of the primary evidences that we have been saved comes from the fact that we love the brethren. In fact, love for the brethren is a constant theme throughout much of the epistle's early chapters:
1 John 2:9–10 (ESV) — 9 Whoever says he is in the light and hates his brother is still in darkness. 10 Whoever loves his brother abides in the light, and in him there is no cause for stumbling.
1 John 3:14–16 (ESV) — 14 We know that we have passed out of death into life, because we love the brothers. Whoever does not love abides in death. 15 Everyone who hates his brother is a murderer, and you know that no murderer has eternal life abiding in him. 16 By this we know love, that he laid down his life for us, and we ought to lay down our lives for the brothers.
Matthew 25:31–46 (ESV) — 31 “When the Son of Man comes in his glory, and all the angels with him, then he will sit on his glorious throne. 32 Before him will be gathered all the nations, and he will separate people one from another as a shepherd separates the sheep from the goats. 33 And he will place the sheep on his right, but the goats on the left. 34 Then the King will say to those on his right, ‘Come, you who are blessed by my Father, inherit the kingdom prepared for you from the foundation of the world. 35 For I was hungry and you gave me food, I was thirsty and you gave me drink, I was a stranger and you welcomed me, 36 I was naked and you clothed me, I was sick and you visited me, I was in prison and you came to me.’ 37 Then the righteous will answer him, saying, ‘Lord, when did we see you hungry and feed you, or thirsty and give you drink? 38 And when did we see you a stranger and welcome you, or naked and clothe you? 39 And when did we see you sick or in prison and visit you?’ 40 And the King will answer them, ‘Truly, I say to you, as you did it to one of the least of these my brothers, you did it to me.’ 41 “Then he will say to those on his left, ‘Depart from me, you cursed, into the eternal fire prepared for the devil and his angels. 42 For I was hungry and you gave me no food, I was thirsty and you gave me no drink, 43 I was a stranger and you did not welcome me, naked and you did not clothe me, sick and in prison and you did not visit me.’ 44 Then they also will answer, saying, ‘Lord, when did we see you hungry or thirsty or a stranger or naked or sick or in prison, and did not minister to you?’ 45 Then he will answer them, saying, ‘Truly, I say to you, as you did not do it to one of the least of these, you did not do it to me.’ 46 And these will go away into eternal punishment, but the righteous into eternal life.”