“Therefore, if you bring your gift to the altar, and there remember that your brother has something against you, leave your gift there before the altar, and go your way. First be reconciled to your brother, and then come and offer your gift.”
In Jesus’ day, people brought gifts to the Priests, as a way of showing God their gratitude and love. Today, our gift to God is our entire lives. Romans 12:1 tells us to offer our bodies as a living sacrifice to God. Yet, Jesus has set before us standard of love to others. Remember that song, "They will know we are Christians by our love."?
I once had a falling out with someone. I really was fine with the whole thing. But the other person was not. Whenever I would try to pray and become intimate with God, I would feel a little prick in my heart that I needed to make amends with this person. Even though I didn't feel offended or think I had done anything wrong, I needed to extend the olive branch her way. I needed to apologize for the way it came across to her in a way that made it right for her.
Jesus is saying, before you come and tell God how much you love him, make up with those who are angry with you. Notice it doesn’t say, that if you are angry with someone, it says “if someone has something against you.”
If you know that someone is mad at you for something you did - even if it was years and years ago. And you have not gone to apologize, then you really haven't walked in love towards that person. Even if the reason they are mad seems ridiculous to you, even if the thing they have against you doesn’t seem right to you, you should ask for forgiveness for hurting them. But especially when you know that the thing you have done was wrong - as hard as it is - you must apologize. Repent for the hurt you caused, even if it was unintentional. Do it for God, to show Him how much you love Him. Jesus says that we show our love for God by obeying Him - and obedience to Him means loving others. So, that means that we show our love for God by loving others!
Send a letter, a gift, call them, or go for a visit. If it’s a family member living in your house that has something against you, repent today. Make your peace, and then you will be loving God with all your heart soul and mind.