The First Reading and Gospel are related because in the Gospel, we see Jesus commanding his disciples to Go into all the world and proclaim the good news to the whole creation and the First Reading shows John and Peter being persecuted by the council.
Persecution always accompanies the preaching of the Gospel. Peter and John show us what to do when confronted with persecution. To not back down and continue to preach the Word. The council could not do anything because the proof was there, so they just warned the two not to speak to anyone in this name. Peter responds by saying: we cannot keep from speaking about what we have seen and heard.
We are called to preach the good news to the whole creation. The good news is the name of Jesus, nothing else. There is no need for gimmicks, or for long winded stories to entertain people. We proclaim the Name of Jesus and nothing else.
Mary Magdalene showed how this is done. She went out and told those who had been with him, while they were mourning and weeping. She spoke of the resurrection of Jesus. But the disciples did not believe her. When we proclaim the Gospel, it is not our problem whether people believe what we proclaim or not. The command of Jesus is to proclaim the good news. If people believe, praise God. If no one believes, praise God. Mother Teresa of Calcutta said we are not called to be successful, but we are called to be faithful.
Fidelity to the message is not diluting the message, making it palatable for people. We speak the truth whether people like it or not, confident that Jesus is with us. Should we be persecuted, or harmed, or even killed, we pray we will have the courage to persevere and trust Jesus will deliver us from harm and give us eternal life. I personally do not now how I will react when confronted in these situations, but we know, God will not lack in giving us what we need. It will be my decision whether I will trust God enough to continue doing what is right or to compromise.
Lord, you told us to go and proclaim the good news. May I have courage to speak the truth even when persecutions or threats to my person comes. May I always proclaim you and not myself or my ideas.