John Piper writes:
These, then, are two great incentives from Jesus to become a World Christian and to dedicate yourself to the cause of Frontier Missions as the twentieth century comes to a close.
1. Every impossibility with men is possible with God (Mark 10:27). The conversion of hardened sinners will be the work of God and will accord with his sovereign plan. We need not fear or fret over our weakness. The battle is the Lord's and he will give the victory.
2. Christ promises to work for us and to be for us so much that when our missionary life is over, we will not be able to say we've sacrificed anything (Mark 10:29-30). When we follow his missionary prescription, we discover that even the painful side-effects work to improve our condition. Our spiritual health, our joy, improves a hundredfold. And when we die, we do not die. We gain eternal life.
Desiring God, 25th Anniversary Reference Edition, (Colorado Springs, CO: Multnomah, 2011), 250.