Why?
The gospel.
The word gospel means good news. It is the good news that Jesus Christ came to earth, revealed Father God to us through his actions and teaching, was crucified, and has risen again so that whoever believes and trusts in him may be saved from their sins. The Bible
tells us that Jesus Christ is the one and only Son of God. He lived a perfect, sinless life and told us that he came to bring peace between us and God. He came to earth to rescue us from our sins. Sin is our rebellion against God and as a result sin separates us from a relationship with God. Sinful rebellion against God puts us under His just wrath and for that we deserve spiritual death and separation from him. We are all sinners and have no power in ourselves to restore the broken relationship between ourselves and God. This is why Jesus Christ reached down to us. He took our sins and the wrath justly due us by being crucified on a cross to pay our punishment for sin. He was buried but after three days he rose from the grave and was seen by hundreds of witnesses. He ascended into heaven where he is now preparing a place for everyone who believes to be with him eternally.
Salvation is the free gift from God. Though we are sinners, Christ died for us in our place to take our punishment for sin. This is called grace because Jesus lovingly gave of Himself for us even though we do not deserve it. Salvation, then, comes from God and God alone. Men and women can be saved by believing in what Christ did on the cross, asking forgiveness for our sins, and trusting Jesus Christ to be our Savior and Lord. There is no sin too big that God cannot forgive or anyone so sinful that He will not save. Salvation is His free gift to all who simply accept it and surrender to him.
Before Jesus returned to the Father he commanded his followers to “go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you.” This means that this gospel is for all people and nations of the earth. This is why we joyfully seek to share the gospel with all people.