Paul sums up what he has been talking about in chapter 14 in this passage. He starts by saying,
We who are strong ought to bear with the failings of the weak and not to please ourselves. Each of us should please his neighbor for his good to build him up. (1-2)
Basically, the “weak” here are those with tender consciences which don’t allow them to do things that are actually okay, or on the other hand require them to do certain things that they don’t have to do. We saw this in Romans 14.
The strong are those who don’t have those limitations or feelings of obligation.
But Paul says those who are strong should not condemn those who are weak. Rather, they should look out for the good of those who are weak to build them up.
He then points to the example of Jesus, who though he was strong, put up with us who were weak. He put up with a squabbling group of disciples who were selfish, self-seeking, proud, and in general a mess. And he served them, even going so far as to wash their dirty feet (John 13).
More, he put up with people that hated him for no reason, who insulted him, and ultimately crucified him, and he interceded for them, praying, “Father forgive them for they know not what they do.”
And then he died in their place, taking the punishment they deserved.
Now all of us, both Jew and Gentile, have reason for hope, because 2000 years ago, Jesus laid his life down for us.
So Paul tells us,
Accept one another, then, just as Christ accepted you, in order to bring praise to God (7).
And he prayed,
May the God who gives endurance and encouragement give you a spirit of unity among yourselves as you follow Christ Jesus, so that with one heart and mouth you may glorify the God and Father of our Lord Jesus Christ. (5)
God calls us to live as one. And the key to that is not to focus on each other and our respective failings, but to focus on Jesus Christ, keeping our eyes on him, and following after him. To the degree that we do focus on each other, it should be not to tear each other down, but to build each other up.
How it must tear at the heart of the Father to see his children biting and devouring each other. Let us not be that way. Let us live as Christ did, putting up with each other, loving and accepting each other, and serving one another.