Jesus commands us to labor for the food which endures more than just a short time — food which endures to everlasting life. He tells us also not to give ourselves in idolatrous labor for that food which necessarily perishes.
Jesus says that the Son of man will give us the bread that does not perish because God the Father has sealed Him, and gloriously honored Him beyond every name that can be given. Because of this, we honor the name of Jesus Christ as well.
But how do we work for this bread? the disciples wondered. Jesus answered that the work which the Father does in us is that we believe in Jesus Christ.
So you are to feed, by faith. You are to sit down at this table, by faith. You are to meditate on the meaning of the table, by faith. You are to eat, by faith.
In a very real sense it is true that we are what we eat. If, by faith, You feed upon the Faithful One, then God multiplies His grace to you and in you. If you show contempt for Him in your partaking, then God uses the Table as a moment of judgment. But no sinner ought to want to hasten any day of judgment at all. Rather, we look to the one who received judgment on our behalf in His death on the cross. We look away from ourselves, and away from our own faithlessness, and to the One who gave Himself for sinners.
So look, now, in faith, and you will see the food of the gospel.