“God’s future grace toward us was purchased and guaranteed by His past grace toward us in Jesus’ death and resurrection. As we have seen, Paul says this in one of the greatest verses in the Bible. ‘He who did not spare His own Son but gave Him up for us all (past grace), how will He not also with Him graciously give us all things (future grace)?’ (Romans 8:32)
Notice the glorious logic of heaven: Because God spared His Son no pain in saving us, therefore He will spare no omnipotent effort to give us all that we need forever. Absolutely certain future grace will come to those who trust Christ, because God infallibly secured it in not sparing His Son.”
–John Piper, Battling Unbelief (Colorado Springs, Co.: Multnomah Publishers, 2007), pp. 17-18.