They ceased not to teach and preach Jesus Christ

 "Go ye therefore, and teach all nations" - Matthew 28:19 KJV

"And daily in the temple, and in every house, they ceased not to teach and preach Jesus Christ." - Acts 5:42 KJV

Jesus commanded His disciples to teach all nations. His disciples were faithful to follow His command. Even when they suffered persecution, they were determined to teach and preach Jesus.

When Jesus first poured out His Spirit on the Day of Pentecost, Peter preached the gospel. He then told the people what they should do.

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost." - Acts 2:38 KJV

"Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls." - Acts 2:41 KJV

"And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers." - Acts 2:42 KJV

They were called, chosen, and faithful. (Revelation 17:14).

“And the Lord added to the church daily such as should be saved." - Acts 2:47 KJV

The disciples continued to preach Jesus and through Him the resurrection from the dead. (Acts 4:2, Acts 4:10-12, 4:33, Acts 5:28). They were threatened and repeatedly put in jail. (Acts 4:3, 4:21, Acts 5:18-20, 5:33). They were commanded to not speak nor teach in the name of Jesus. (Acts 4:17,18, Acts 5:40).

"Then Peter and the other apostles answered and said, We ought to obey God rather than men. The God of our fathers raised up Jesus, whom ye slew and hanged on a tree. Him hath God exalted with his right hand to be a Prince and a Saviour, for to give repentance to Israel, and forgiveness of sins. And we are his witnesses of these things; and so is also the Holy Ghost, whom God hath given to them that obey him. 

“When they heard that, they were cut to the heart, and took counsel to slay them." - Acts 5:29-33 KJV

Gamaliel spoke to the council. 

"And to him they agreed: and when they had called the apostles, and beaten them, they commanded that they should not speak in the name of Jesus, and let them go." - Acts 5:40 KJV

"And they departed from the presence of the council, rejoicing that they were counted worthy to suffer shame for his name. And daily in the temple, and in every house, they ceased not to teach and preach Jesus Christ." - Acts 5:41-42 KJV