Preaching the Gospel of Jesus Christ to a lost and dying world is truly a privilege as well as a commission.
Through Scripture, Paul teaches us that the power of God unto salvation begins with hearing the Word of God.
God's Word is alive and it has a transforming effect on lives when it is spoken or read. It is true that God's Word does not return void, for whenever or wherever His Word goes forth there is always a reaction.

The majority of Christ's preaching was done outside of the synagogue. From the Mount of Olives, to a boat in the middle of the sea, hillside or street side, Christ preached to the people using parables and the Old Testament to explain the Kingdom of God, sin, repentance and judgment, as well as the remedy for sin - righteousness in Christ.
The spirit of the law and the true interpretation of the written Word is what Christ taught.