Where in the Bible does God turn stone to bread?

Nowhere.

Jesus was tempted to turn stone into bread to prove He is the Son of God, but He resisted that temptation.

http://www.biblegateway.com/passage/?search=matt%204:3&version=51

http://www.biblegateway.com/passage/?search=luke%204:3;&version=51;

Why then does Willie Nelson sing this in the song "We Are The World"?

http://www.youtube.com/watch?v=k2W4-0qUdHY&feature=related

See here:

"Remember when Willie Nelson gets his moment in the sun and comes in with his signature warble? He says: “As God has shown us… by turning stone to bread…” I’ll never forget hearing that for the first time. For me it was like hearing someone referring to President Richard M. Dixon. I couldn’t believe it. Had Willie Nelson just said that God had at one time “turned stone to bread”? Had I really heard that? Who’d written this lyric — and why had Willie sung it? I could only guess that the lyricist was Lionel Ritchie or the King of Pop himself. In any case, they had flubbed up rather majorly here. It was obvious that they mistakenly thought Jesus had at some point in his ministry performed this miracle… But as any non-Grammy-winning Fifth-grader knows from Sunday School, Jesus didn’t turn stone to bread — he refused to turn stone to bread. That’s an important difference ... Certainly no one in the news media picked up on this whopping gaffe at the time, and as far as I know it’s never been mentioned since. Why? Well, mainly because the tiny group of Americans who are part of the much-vaunted media elites simply don’t know this sort of thing. And here’s the kicker — they don’t know anyone who knows it ..."

http://ericmetaxas.com/writing/essays/theyre-not-world-theyre-bubble-people/

In several spots, the Bible alludes to the seemingly spontaneous generation of food. While stone is not turned to bread, Psalm 104 does give God the credit for bringing "bread from the earth". In Numbers 19 God brings forth water from seemingly otherwise barren rock. In Exodus, the manner in which the mannah is formed is described as it's being formed from lifeless dewdrops.