Jesus denies that the children of Israel were given bread or manna from heaven by Moses. Jesus also does not attribute bread or manna from heaven as coming from his own Father. In John 6, Jesus makes this abundantly clear, even after the inquirers said correctly, “Our fathers ate the manna in the wilderness; as it has been written, ‘He gave them bread from heaven to eat.'” They were quoting from Ex 16:21. How can this be true and not true at the same time?
Jesus does not attribute this to Moses because it wasn’t Moses who accomplished the giving of manna in the first place. Christ does not attribute the giving of manna to the Father, perhaps because it was the pre-incarnate Son, Jesus Himself, who fed them with manna. The activity of the Son in the Old Testament, especially with the Israelites in the wilderness is clearly attested, in my view. Another consideration is that the “heaven” Jesus is emphasizing when He speaks of His origin, is the heaven of heavens where the Father rules. The heaven referred to in Exodus from which the Israelites received their manna was the atmospheric heaven. It came down like the dew.
But the main point is this: Jesus is the true bread of heaven sent from the Father. To disbelieve this is to not only misunderstand Christ and Christianity, but to essentially be an unbeliever.
“Jesus then said to them, ‘Truly, truly, I say to you, it is not Moses who has given you the bread out of heaven, but it is the Father who gives you the true bread out of heaven. For the bread of God is that which comes down out of heaven, and gives life to the world . . . I am the bread of life” (Jn 6:32-35).
You may wish to listen to the following instruction concerning appearances of Christ in the OT. http://www.sermonaudio.com/sermoninfo.asp?SID=112121129502