Jesus is the provider and sustainer for all human needs. Most importantly Jesus came to give us eternal life. Therefore, God the Father has placed HIS seal of approval on Jesus. John uses the technical term for seal meaning ‘to certify’. In John 3:33 the same term is used saying that when ‘we’ accept Jesus’ message, we ‘certify’ God is true. Here Jesus is making it clear that we need to work for the food that provides eternal sustenance which only HE can provide.