Joe Thorn wrote what motivations mission from a reformed perspective:
Man’s total depravity moves me to preach Jesus Christ because I know that there is no hope (Eph 2.12) for a man to find his way to God, accidentally or intentionally, on his own. There is no hope of him believing the truth apart from the preaching of the Gospel (Rom 10.14-15). Because people are dead in their sins (Eph 2.1), and are unwilling to come to Christ apart from the Father’s drawing (Jn 6.44), I know that their salvation hinges on God’s sovereign work (Eph 2.9). I know that he uses the preaching of the Gospel as the means of awaking the dead (Ezk 37).
The doctrine of election encourages me to share the Gospel, because I am assured that God has chosen a people (Eph 1.3-6) for himself. Like Jesus, the prophets and the Apostles, I preach indiscriminately to all, trusting that all who were predestined to eternal life will believe (Acts 13.48), if not now, later.
Particular redemption compels me to tell others about Jesus because not a drop of Christ’s blood was wasted. Because Jesus has purchased people from every tribe, tongue and nation (Rev 5.9) we understand that God has sent us where we are, and is sending others around the world to preach Christ crucified with the awareness that He is building his church. Christ has accomplished redemption for his people (Mt 1.21; Jn 19.30; Eph 5.25-27; Heb 1.3), and it only awaits application.
The doctrine of effectual grace pushes me out of my study and into the community with the Gospel because I know that, although I may fail to persuade someone, God will not (Phil 1.6). Because a leopard cannot change his spots, nor man his nature (Jer 13.23), I am relieved to know that God will cause a man to be born again (1 Pet 1.3). So I tell as many as I am able the good news that we have in Jesus, with the hope that God will open hearts to respond to the word (Acts 16.14).