The priests arrest Peter and John, but not before many believe in Jesus, from the speech in chapter 3. The next morning they interrogate Peter and John, which gives another example to witness to Christ. They can't deny the miracle, but oppose the message, and so forbid them to speak of Jesus anymore. Peter refuses to their face, and. They threaten and let them go.
They go back to the church, and the church prays together, quoting and applying Psalm 2 to their situation: the rulers are opposing Christ, but that won't stop God. They ask for more boldness, and God answers by shaking the place with the Spirit. The church continues in generosity together. Selling land may also mean a shift from looking to promises for land in Israel, to seeing God's people re-constituted with the apostles as her true leaders.
How this is about Jesus
On the surface the main story is the boldness of the apostles, but the real dispute is about Jesus. The rulers thought Je would go away once they killed Him, and we tend to think the tension between Jesus and earthly rulers has gone away since Jesus ascended, but it has not.
An important principle comes clear from verse 19: earthly rule and authority is fallible and must be opposed when it opposes Christ. Whether in church, state or home, the Bible abounds with examples of godly resistance or disobedience to wicked authority. The Hebrew midwives in Egypt, Rahab in Jericho, Abigail with David against Nabal, several Judges, Daniel in Babylon. We usually limit this civil disobedience to times when the authority that forces us to directly disobey God, requiring us to disobey them, as here in Acts 4. But Rahab and Abigail are instances that go beyond that, where we are not forced by the ruler and thus required by God to civil disobedience, yet we MAY proactively initiate opposition to them, to avert great harm.
Paul also often prays for boldness, knowing the great opposition to the Gospel in the world. Are we willing to speak in Christ's name, knowing the ridicule and hostility that will result?