Have you ever asked yourself, "Why should I witness?" Several reasons should come to mind. First, because Jesus commands you to: "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit (Matt. 28:19). Also, Ezekiel 3:11 says, "and go to the exiles, to the sons of your people, and speak to them and tell them, whether they listen or not..."
Second, you must witness because you love the unsaved (if you don't, you should). The most loving thing you can do is present the gospel in hopes of bringing others to salvation. Galatians 5:22 lists love as one of the fruits of the Spirit. It is love's nature to give. Take for example John 3:16, "For God so loved the world that He gave His only begotten Son..." Love gives, and if you have only a small portion of His love, you will want to give to others.
Third, witness because it is a wise thing to do. Proverbs 11:30 says, "...he who is wise wins souls." Now, I know I am not a very wise person. But, since God says I'll be wise to win souls, or try to, then great, let me at it. I want to be wise in God's sight.
Fourth, witness to keep people out of hell. Hell is a terrifying place of utter anguish and eternal separation from God. Those who are not saved go there. Witnessing is an attempt to keep them out of hell.
And finally, and most important, witness so they may find the love and fellowship of God (1 John 1:3), the greatest of all treasures. I can think of no greater gift than salvation. It frees the sinner from sin, it delivers the lost from damnation, and it reveals the true and living God to those who don't know Him.
The angels of heaven rejoice greatly when anyone passes from judgment into salvation (Luke 15:10). Shouldn't we as Christians rejoice too? Shouldn't we weep over the lost? Shouldn't we ask the Lord of the field to send laborers into His harvest (Luke 10:2)? Certainly! The salvation of others is the goal of your efforts. The love of God is your motive. Is there anything greater? So, give.