1. They preached that Jesus was raised from the dead. The Sadducees denied the resurrection and the official line was that his body had been stolen.
Acts 4:1 And as they spake unto the people, the priests, and the captain of the temple, and the Sadducees, came upon them, 2 Being grieved that they taught the people, and preached through Jesus the resurrection from the dead.
Acts 23:8 For the Sadducees say that there is no resurrection, neither angel, nor spirit…
Matthew 28:12 And when they were assembled with the elders, and had taken counsel, they gave large money unto the soldiers, 13 Saying, Say ye, His disciples came by night, and stole him away while we slept. 14 And if this come to the governor’s ears, we will persuade him, and secure you. 15 So they took the money, and did as they were taught: and this saying is commonly reported among the Jews until this day.
2. That the Jewish leaders had unjustly crucified Jesus and God had made him the chief corner stone.
Acts 4:10. Be it known unto you all, and to all the people of Israel, that by the name of Jesus Christ of Nazareth, whom ye crucified, whom God raised from the dead, even by him doth this man stand here before you whole. 11 This is the stone which was set at nought of you builders, which is become the head of the corner.
Acts 5:28 Saying, Did not we straitly command you that ye should not teach in this name? and, behold, ye have filled Jerusalem with your doctrine, and intend to bring this man’s blood upon us.
3. That Salvation was only possible through Christ and not through the Law of Moses.
Acts 4:12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.
I hope you find this helpful.