Jesus was sharing here that He was about to die and rise again. He begins the passage with "The hour has come for you to see the Son of Man glorified." He is reassuring them ( the disciples) and US that to LIVE, we must die. When Jesus died on the cross and was resurrected, He produced many seeds. I love that Jesus uses the example of the wheat. It falls to the ground and dies, but then it grows in the soil, producing many more seeds. He uses this example to illustrate what will happen to Him, but then, extends it to us.
We must die to live.
Die to our flesh.
Die to our own selfish desires.
Die to sin.
