John 6:28 - Matthew Poole's English Annotations on the Holy Bible

They easily understood that our Saviour did not speak of any worldly food, by his opposing the labour he mentions, and persuadeth for, to a labour for the world; but still they did not understand what labour he spake of, but dreamed of the works of the law; knowing of no other work which God commanded, but which was prescribed in the law; and they (probably) being some, or many of them, strict observers, especially of the law contained in ordinances, and probably many of them of the moral law also, according to the sense of it given by their teachers; in which sense the young man, Matthew 19:20, being bid by our Saviour to keep the law, and naming most of the precepts of the second table, told him, All these things have I kept from my youth: what lack I yet? They wondered what works our Saviour meant; what labour, when he said, Labour for that bread, or that meat which endureth to everlasting life; thinking that those who kept the law (in the sense before expressed) had no more to do.