Lord, when saw we thee an hungred, and fed thee? or thirsty, and gave thee drink? When saw we thee a stranger, and took thee in? or naked, and clothed thee? Or when saw we thee sick, or in prison, and came unto thee? (Matt. 25: 37-39)
One thing I love about this text from Matthew 25 is that the "sheep," the righteous whom Christ welcomes into his rest at the last day, don't seem to have had any idea that they were in Christ's service during their mortal life time. "When saw we thee?" they ask again and again. They didn't know that Christ was in the persons of their fellow human beings. It had to be explained to them at the final judgment, when the reason for their exaltation comes to them as a complete surprise. Apparently they fed the hungry, took in the stranger, clothed the naked, and visited the sick and imprisoned out of a love for their fellow man, not out of a desire to please God, whom they literally did not see.
One reason this becomes such a powerful statement about the nature of exaltation is because it emphasizes that the sole, ultimate criterion is not whom you think you are serving, but that you serve. It emphasizes that charity, pure love, is the quality that aligns us with the Kingdom of God, not whether or not we see Christ in this life. The seeing of Christ described here is metaphorical. Is believing a form of seeing? I think so. The text definitely suggests that exaltation is not a matter of belief. It is not dependent on whether we see Christ in our suffering fellow humans. It is purely and solely a matter of compassion for one's fellow human beings, compassion that motivates us to act.
Believers who serve their fellow human beings because they've read this text and are eager to be among the sheep are not necessarily described in this text. In fact, I would argue that someone who serves their fellow human beings solely because of concern with reward in the next life has utterly missed the point here. I think the teaching at the heart of this text is that love for the sake of love is the love that exalts. I think that's the true meaning of the text that says, "Whosoever shall seek to save his life shall lose it" (Luke 17: 33). You can't be saved, if the reason for your behavior is to be saved, to avoid damnation. You've missed the point if that is your motivation.
Another text that I think is relevant to the problem of belief is the parable of the two sons in Matthew 21: 28-31. Here, profession is at the core of the problem. It is what distinguishes one son from the other. One son professes that he will serve his father. But he does not. The other son professes that he will not serve his father. But he shows up and serves anyway. Christ asks the Pharisees which of these sons are righteous, and they are compelled to answer, the son who actually showed up for work despite his profession to the contrary. Christ then ends by delivering the shocking moral: "The publicans and the harlots go into the kingdom of God before you." Again, this teaching suggests that profession is irrelevant to exaltation.
As an outcast homosexual, I think about this a lot. I will be a witness at the last day of the kindness and compassion shown me by people who professed no belief in God, contrasted with the hardness of heart of those who profess belief and a love for God. Believers so often pick and choose whom they will serve. The "worthy" poor are a favorite target for charity. Jesus didn't seem to make any such distinction. He anticipated seeing harlots and publicans in Heaven before good, righteous believers.