We are witnesses of these things, and so is the Holy Spirit, whom God has given to those who obey him

Acts 5:17-42

Then the high priest and all his associates, who were members of the party of the Sadducees, were filled with jealousy. They arrested the apostles and put them in the public jail. But during the night an angel of the Lord opened the doors of the jail and brought them out. “Go, stand in the temple courts,” he said, “and tell the people all about this new life.”

Then someone came and said, “Look! The men you put in jail are standing in the temple courts teaching the people.” At that, the captain went with his officers and brought the apostles. They did not use force, because they feared that the people would stone them.

Peter and the other apostles replied: “We must obey God rather than human beings! The God of our ancestors raised Jesus from the dead—whom you killed by hanging him on a cross. God exalted him to his own right hand as Prince and Savior that he might bring Israel to repentance and forgive their sins. We are witnesses of these things, and so is the Holy Spirit, whom God has given to those who obey him.”

But a Pharisee named Gamaliel, a teacher of the law, who was honored by all the people, stood up in the Sanhedrin and ordered that the men be put outside for a little while. Then he addressed the Sanhedrin: “Men of Israel, consider carefully what you intend to do to these men. 

Therefore, in the present case I advise you: Leave these men alone! Let them go! For if their purpose or activity is of human origin, it will fail. But if it is from God, you will not be able to stop these men; you will only find yourselves fighting against God.”

The apostles left the Sanhedrin, rejoicing because they had been counted worthy of suffering disgrace for the Name. Day after day, in the temple courts and from house to house, they never stopped teaching and proclaiming the good news that Jesus is the Messiah.

Why?

The high priest and all his associates were filled with jealousy, for they killed Jesus and the apostles taught the people to trust in Jesus.

It is the Lord helped the apostles, the door of jail did not open but the apostles were out of jail. 

Gamaliel is comfortable speaking the truth, if apostles's activity is of human origin, they will fail, but if it is from God, you will not be able to stop these men, and you will find yourselves fighting against God.

How?

If our activity comes from the Lord, no one can stop us, if our activity comes from human origin, it will fail.