I think that we are struggling with (I certainly have been) ... the mentions of "servants" being consigned to "outer darkness".
My current thought on these passages ... is that these passages refer to those who considered themselves to be servants of God within Israel, ... who, in part, failed to stick with God's program (i.e. accept and support the Messiah).
I believe the servant of the master is a servant of God. The Bible gives many examples of people who will not be saved because of their actions. Here’s a few examples.
I am the true grapevine, and my Father is the gardener. He cuts off every branch of mine that doesn’t produce fruit, and he prunes the branches that do bear fruit so they will produce even more. You have already been pruned and purified by the message I have given you. Remain in me, and I will remain in you. For a branch cannot produce fruit if it is severed from the vine, and you cannot be fruitful unless you remain in me. “Yes, I am the vine; you are the branches. Those who remain in me, and I in them, will produce much fruit. For apart from me you can do nothing. Anyone who does not remain in me is thrown away like a useless branch and withers. Such branches are gathered into a pile to be burned.
John 15:1-6
When you follow the desires of your sinful nature, the results are very clear: sexual immorality, impurity, lustful pleasures, idolatry, sorcery, hostility, quarreling, jealousy, outbursts of anger, selfish ambition, dissension, division, envy, drunkenness, wild parties, and other sins like these. Let me tell you again, as I have before, that anyone living that sort of life will not inherit the Kingdom of God.
Galatians 5:19-21
Even now the ax of God’s judgment is poised, ready to sever the roots of the trees. Yes, every tree that does not produce good fruit will be chopped down and thrown into the fire.
Matthew 3:10
Nothing evil will be allowed to enter, nor anyone who practices shameful idolatry and dishonesty—but only those whose names are written in the Lamb’s Book of Life.
Revelation 21:27
Let there be no sexual immorality, impurity, or greed among you. Such sins have no place among God’s people. Obscene stories, foolish talk, and coarse jokes—these are not for you. Instead, let there be thankfulness to God. You can be sure that no immoral, impure, or greedy person will inherit the Kingdom of Christ and of God. For a greedy person is an idolater, worshiping the things of this world. Don’t be fooled by those who try to excuse these sins, for the anger of God will fall on all who disobey him.
Ephesians 5:3-6
But when the Son of Man comes in his glory, and all the angels with him, then he will sit upon his glorious throne. All the nations will be gathered in his presence, and he will separate the people as a shepherd separates the sheep from the goats. He will place the sheep at his right hand and the goats at his left. “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 creation of the world. For I was hungry, and you fed me. I was thirsty, and you gave me a drink. I was a stranger, and you invited me into your home. I was naked, and you gave me clothing. I was sick, and you cared for me. I was in prison, and you visited me.’ “Then these righteous ones will reply, ‘Lord, when did we ever see you hungry and feed you? Or thirsty and give you something to drink? Or a stranger and show you hospitality? Or naked and give you clothing? When did we ever see you sick or in prison and visit you?’ “And the King will say, ‘I tell you the truth, when you did it to one of the least of these my brothers and sisters, you were doing it to me!’ “Then the King will turn to those on the left and say, ‘Away with you, you cursed ones, into the eternal fire prepared for the devil and his demons. For I was hungry, and you didn’t feed me. I was thirsty, and you didn’t give me a drink. I was a stranger, and you didn’t invite me into your home. I was naked, and you didn’t give me clothing. I was sick and in prison, and you didn’t visit me.’ “Then they will reply, ‘Lord, when did we ever see you hungry or thirsty or a stranger or naked or sick or in prison, and not help you?’ “And he will answer, ‘I tell you the truth, when you refused to help the least of these my brothers and sisters, you were refusing to help me.’ “And they will go away into eternal punishment, but the righteous will go into eternal life.
Matthew 25:31-46
Jesus replied, “The Son of Man is the farmer who plants the good seed. The field is the world, and the good seed represents the people of the Kingdom. The weeds are the people who belong to the evil one. The enemy who planted the weeds among the wheat is the devil. The harvest is the end of the world, and the harvesters are the angels. “Just as the weeds are sorted out and burned in the fire, so it will be at the end of the world. The Son of Man will send his angels, and they will remove from his Kingdom everything that causes sin and all who do evil. And the angels will throw them into the fiery furnace, where there will be weeping and gnashing of teeth. Then the righteous will shine like the sun in their Father’s Kingdom. Anyone with ears to hear should listen and understand!
Matthew 13:37-43
A faithful, sensible servant is one to whom the master can give the responsibility of managing his other household servants and feeding them. If the master returns and finds that the servant has done a good job, there will be a reward. I tell you the truth, the master will put that servant in charge of all he owns. But what if the servant is evil and thinks, ‘My master won’t be back for a while,’ and he begins beating the other servants, partying, and getting drunk? The master will return unannounced and unexpected, and he will cut the servant to pieces and assign him a place with the hypocrites. In that place there will be weeping and gnashing of teeth.
Matthew 24:45-51
All who are victorious will inherit all these blessings, and I will be their God, and they will be my children. “But cowards, unbelievers, the corrupt, murderers, the immoral, those who practice witchcraft, idol worshipers, and all liars—their fate is in the fiery lake of burning sulfur. This is the second death.
Revelation 21:7-8
Then he said, “I tell you the truth, unless you turn from your sins and become like little children, you will never get into the Kingdom of Heaven. So anyone who becomes as humble as this little child is the greatest in the Kingdom of Heaven. “And anyone who welcomes a little child like this on my behalf is welcoming me. But if you cause one of these little ones who trusts in me to fall into sin, it would be better for you to have a large millstone tied around your neck and be drowned in the depths of the sea. “What sorrow awaits the world, because it tempts people to sin. Temptations are inevitable, but what sorrow awaits the person who does the tempting. So if your hand or foot causes you to sin, cut it off and throw it away. It’s better to enter eternal life with only one hand or one foot than to be thrown into eternal fire with both of your hands and feet. And if your eye causes you to sin, gouge it out and throw it away. It’s better to enter eternal life with only one eye than to have two eyes and be thrown into the fire of hell.
Matthew 18:3-10
None of these examples give any indication of excluding believers. They all apply to everyone believers included.
