“Iesus answered, and said vnto them, This is the worke of God, that ye beleeue on him whom he hath sent.”
1611 King James Version (KJV)
6:29 This is the work of God - The work most pleasing to God, and the foundation of all others: that ye believe - He expresses it first properly, afterward figuratively.
Joh 6:29 This is the work of God, that ye believe on him whom he hath sent. They are startled by hearing that to please God the first requirement is faith in Christ. This is "the work of God" that pleases him. "Without faith it is impossible to please God" (Heb 11:6). It is not "works", but one work, that is required, a faith that would enable them to lay hold upon him who is the Bread of Life. From such faith would spring a Christlike life.