Mark 8:31 (NET) Then Jesus began to teach them that the Son of Man must suffer many things and be rejected by the elders, chief priests, and experts in the law, and be killed, and after three days rise again. 32 He spoke openly about this. So Peter took him aside and began to rebuke him. 33 But after turning and looking at his disciples, he rebuked Peter and said, “Get behind me, Satan. You are not setting your mind on God’s interests, but on man’s.”
Suffering is an essential part of life
Gain involves suffering. Do you want to get in shape? Prepare to suffer the pain of exercise. Do you want to achieve a healthy weight? Prepare to suffer the deprivation of some tasty foods. Do you want to learn? Prepare to suffer the discipline of study. Do you want strong, healthy friendships? Prepare to suffer being wronged, forgiving, and in some cases, establishing necessary boundaries.
In Jesus case, he wanted to gain a family for eternity. That gain required forgiveness. Securing our forgiveness cost him. He paid our sentence. He died our death. He became the sacrificial lamb.
It was for God’s interests
If Satan had convinced Jesus to escape his suffering, we would be lost. That is why Jesus said to Peter, “Get behind me, Satan.” He recognized Satan was using Peter as a tool to persuade him to abandon his mission to suffer and die in our place, for our sins.
God’s interest was to establish a people for himself. A family for eternity. Jesus suffering and death made it possible and legal. Jesus sacrifice fulfilled God’s legal requirement for our acceptance.
That is what Jesus meant when he said, on the cross, “It is finished.” Finished means completed. When Jesus suffered and died on the cross, all the legal requirements for our acceptance as God’s children were completed.
Dana Roseman's Thoughts on Scripture 