1 Peter 3:8-12 - “Finally, all of you have unity of mind, sympathy, brotherly love, a tender heart, and a humble mind. Do not repay evil for evil or reviling for reviling, but on the contrary, bless, for to this you were called, that you may obtain a blessing. For ‘Whoever desires to love life and see good days, let him keep his tongue from evil and his lips from speaking deceit;let him turn away from evil and do good; let him seek peace and pursue it.For the eyes of the Lord are on the righteous, and his ears are open to their prayer. But the face of the Lord is against those who do evil.’”
John 13:35 - “By this all people will know that you are my disciples, if you have love for one another.”
Galatians 6:7 - “Do not be deceived: God is not mocked, for whatever one sows, that will he also reap.”
How we treat other believers reflects our faith in Christ, or lack thereof.