To paraphrase verse 1-2: Since there is (great) encouragement in Christ, comfort from love, participation in the Spirit, affection and sympathy – we should be of the same mind, have the same love, be in full accord and of one mind. This will also bring joy to our spiritual fathers, those who have come before us.
As Jesus has said, “the world will know that you are my disciples if you love one another.”
Not surprisingly, we have an actual opportunity now where we can show our love to our brothers and sisters in Christ. This is God’s reminder to us.
Do nothing from selfish ambition or conceit, but in humility count others more significant than yourselves. Let each of you look not only to his own interests, but also to the interests of others. Have this mind among yourselves, which is yours in Christ Jesus, (Philippians 2:3-5 ESV)