There was once a bridge which spanned a large river. During most of the day the bridge sat with its length running up and down the river; parallel with the banks, allowing ships to pass freely by on both sides of the bridge. But at certain times each day, a train would come by and the bridge would be turned sideways (90 degrees) across the river, allowing a train to cross it.
A switchman sat in a small shack on one side of the river where he operated the controls to turn the bridge and lock it into place as the train crossed. One evening as the switchman was waiting for the last train of the day, he looked off into the distance through the dimming twilight and caught sight of the train lights. He stepped to the controls and waited until the train was within a specified distance, when he was to turn the bridge. He turned the bridge into position, but, to his horror, he found the locking control on the far side of the bridge did NOT work. If the bridge was not securely "locked" it would wobble back and forth at the ends when the train came onto it, causing the train to jump the track and crash into the river.
Worse still, this was a passenger train with many people aboard. Instinctively, he ran across the bridge to the other side of the river where there was a "manual lock" he could apply to hold the bridge tracks in place. He would have to hold the lever firmly as the train crossed. He could hear the rumble of the train now, as he took hold of the lever and leaned backward to apply his full weight to the lever, locking the bridge. He kept applying the pressure to keep the mechanism locked. Many lives depended on this man doing the right thing.
Then, coming across the bridge from the direction of his control shack, he heard a sound that made his blood run cold. "Daddy, where are you?" His four-year-old son was crossing the bridge to look for him. His first impulse was to cry out to the child, "Run! Run!" But the train was too close; the tiny legs would never make it across the bridge in time. The man almost left his lever to run and grab his son and carry him to safety. But he realized that he could not get back to the lever in time. Either the people on the train or his son must die. He had only a moment to make his decision.
The train sped safely and swiftly on its way, and no one aboard was even aware of the tiny broken body thrown mercilessly into the river by the onrushing train. Nor were they aware of the pitiful figure of the sobbing man, still clinging tightly to the locking lever long after the train had passed. They didn't see him walking home more slowly than he had ever walked; to tell his wife how their son had brutally died -- that others may live.
If you can imagine the emotions which went this man's heart, you can begin to understand the feelings of our Father in Heaven when He sacrificed His Son to bridge the gap between us and eternal life. Is it any wonder that He caused the earth to tremble and the skies to darken when His Son died? How do you think God feels as we speed along thru life, without giving a thought to what He did for us by sending His son, Jesus Christ, to die for our sins -- so WE could have eternal life?