Jesus commanded His disciples to go and preach the gospel and make new disciples. Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. 19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.” (Matthew 28:18-20).
"Go into all the world and preach the gospel to all creation. (Mark 16:15).
All this is from God, who reconciled us to himself through Christ and gave us the ministry of reconciliation (2 Corinthians 5:18).
Whilst modern society sometimes objects to being preached at, Christian preaching (the act of publicly and openly broadcasting or proclaiming the gospel of Jesus) is a necessary means to ensure that those who may not otherwise come into contact with a Christian may still get to hear the message of Jesus, thereby affording them the opportunity to receive salvation.
Jesus sent out His disciples in two's to go and share the gospel (The Good News). He also gave them authority over evil spirits so that they may drive them out from those who suffered infirmities. This would often be a demonstrable and irrefutable evidence that there is power in the name of Jesus, and also that Jesus Christ is the Son of God. This would validate the testimonies of the disciples. Calling the Twelve to him, he began to send them out two by two and gave them authority over impure spirits (Mark 6:7). The evidence of the power of God displayed through miracles, healing and the driving out of demons, in the name of Jesus, often drew people into giving their lives to Jesus and become a disciple (a follower of Jesus - a Christian).
Jesus directly affirmed that once a Christian received the Holy Spirit they will be His witness. As such, one of the evidence that a Christian has The Holy Spirit of God is that they actively become a witness of Jesus. But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.” (Acts 1:8)
A 'witness' is defined as - to see, hear, or know by personal experience. Those who are witnesses of Jesus are compelled by The Holy Spirit to testify of one's personal (first hand) encounter of Jesus and to convey why that encounter was so transformative and worthy to be proclaimed publicly even at the risk of being personally mocked or ridiculed. It is the bold witnessing of Jesus by Christians that leads others into the Kingdom of God.
The motivation to be a witness of Jesus to others should be firstly, out of love for Jesus because of the free gift of salvation He gave to us through His death and resurrection. Secondly, it is because we want others to share in the same grace of salvation and divine privileges that we enjoy as Christians (having been spared of condemnation and punishment because Jesus has already paid the full price of our sins). Finally, God wants all people to be saved. I urge, then, first of all, that petitions, prayers, intercession and thanksgiving be made for all people — for kings and all those in authority, that we may live peaceful and quiet lives in all godliness and holiness. This is good, and pleases God our Savior, who wants all people to be saved and to come to a knowledge of the truth. (1 Timothy 2:1-4).
By your active public witnessing of Jesus (evangelising), others will also come to the knowledge of the truth and some will be saved as a direct consequence. Heaven rejoices when a single person is saved. What a joy and delight that God has afforded us such pleasures to be a witness of Jesus Christ and lead the lost to freedom and to eternal life. I tell you that in the same way there will be more rejoicing in heaven over one sinner who repents than over ninety-nine righteous persons who do not need to repent. (Luke 15:7).