1. Praying also for us, that God would open to us a door for the word, to speak the mystery of Christ, (Col 4:3-4)
    Mk 1:38-39, Mk 3:14, Acts 5:42, 1 Cor 1:21, Titus 1:3, Eph 3:3-4, Eph 6:19-20

Evangelism is preaching that Jesus is the Christ prophesied in the Old Testament.

Paul asked the saints to pray so that God could open the door of evangelism to him and tell them that Jesus is the Christ. (Col 4:3-4, Eph 6:19-20)

Col 4:3 Withal praying also for us, that God would open unto us a door of utterance, to speak the mystery of Christ, for which I am also in bonds:
4 That I may make it manifest, as I ought to speak.

Eph 6:19 And for me, that utterance may be given unto me, that I may open my mouth boldly, to make known the mystery of the gospel,
20 For which I am an ambassador in bonds: that therein I may speak boldly, as I ought to speak.

Jesus came to this earth to reveal that He is the Christ. In other words, Jesus came to this earth for evangelism. (Mk 1:38-39)

Mk 1:38 And he said unto them, Let us go into the next towns, that I may preach there also: for therefore came I forth.
39 And he preached in their synagogues throughout all Galilee, and cast out devils.

Jesus sent his disciples to evangelize. (Mk 3:14)

Mk 3:14 And he ordained twelve, that they should be with him, and that he might send them forth to preach,

The early church members evangelized whenever they met. (Acts 5:42)

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

God saves people through evangelism. (1 Cor 1:21, Titus 1:3)

1 Cor 1:21 For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.

Titus 1:3 But hath in due times manifested his word through preaching, which is committed unto me according to the commandment of God our Saviour;

Paul explained to each church that Jesus was the Christ. (Eph 3:3-4)

Eph 3:3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)