Acts: Change the World - Saved by Grace

When some Pharisee Christians wanted to require following the law of Moses, the church leaders said, "No, we are saved by grace." However, they did instruct some things be done. "telling them to abstain from food polluted by idols, from sexual immorality, from the meat of strangled animals and from blood. 21 For Moses has been preached in every city from the earliest times and is read in the synagogues on every Sabbath.” Why these things? Does what we do matter? Is it a matter of conscious? (Romans) However, in Acts 16, Paul circumcised Timothy because of the Jews in the area. Why? (sacrificing our freedoms, abiding by others restrictions all so others may hear the message of Christ.)