Summary: If you are curious about spiritual manifestations, the Bible gives us examples of them.
If it’s of God...
The setting of the text is at a time of great excitement in the life of the church and the disciples. Pentecostal power had recently exploded on the 120 in the upper room, and thousand’s of folks had been getting saved on a daily basis. Sick people were being healed, and demons were being cast out. The empowerment of the Spirit had definitely made its mark on those who had received it.
Bible says in V.12 that the apostles were performing many miraculous signs/wonders among the people. They would meet in a place called Solomon’s porch (Colonade). *This area had become a meeting place of miracles. For, in 3:11 it was the place where Peter & John held to the lame man that was healed while all the people came running to them in amazement at what they had just witnessed. It was where the believers would meet up and listen to the wonderful word of God, while their sick and demon possessed were being delivered/set free. As a matter of fact, V.16 says crowds began to gather from towns around Jerusalem, bringing those who were bound with these physical/spiritual afflictions, and ALL of them were healed.
After a while the high priest and all his associates began to be filled with jealousy. They didn’t want this sort of change because they felt threatened. This stuff went totally beyond their belief systems; they couldn’t comprehend all that was going on. Not to mention the fact that these apostles, who was labeled as ’ignorant and unlearned men’, were doing things for the Lord, that was bringing Him praise/glory, instead of the Sanhedrin.
So they arrested the apostles and put them in the public jail. But suddenly, during the night, an angel of the Lord opened the doors and got them out, saying "Go stand in the temple courts and tell the people the full message of this new life". So at daybreak, they entered the temple courts and did as they were told.
When the high priest arrived, he called for the Sanhedrin to meet together so they could decide what to do about the apostles. He wanted to get rid of them for good. But when they went to get them out of the jail for the trial, they were gone. The jail was securely locked, and the guards were standing at the doors, but no one was inside. They soon found out that these crazy preachers were in the temple courts declaring the word of the Lord.
They immediately went and got the apostles and brought them before the Sanhedrin, saying "We gave you strict orders not to teach in the name of Jesus, but you have done it anyway". Peter & the apostles: "We must obey God rather than men!" *When they heard this, they were furious and decided to put them to death.
There was one Pharisee however who didn’t think this was such a good idea. His name was Gamaliel. He was greatly respected amongst the high council for his wisdom. (teacher of Saul) He was so highly respected that he gained the attention of the Sanhedrin, which was something usually only the High Priest could do. *He had the apostles taken outside for a while, so he could talk about them/this situation in privacy. "We need to carefully consider what we are going to do to these men. You remember when the man named Theudas appeared, claiming to be a real somebody, and about 400 people followed him. It wasn’t long and he was killed and his people dispersed, and his work came to nothing. Remember Judas the Galilean? He appeared in the days of the census and led a band of people in a revolt. He too was killed and his people scattered. Therefore in the present case I advise you to leave these men alone and let them go. For, if their purpose/activity if of the flesh, it will fail. But if it’s from God, you won’t be able to stop these men anyway. All you’ll be doing is finding yourself fighting against God!"