D&C 22

To those early saints that assumed that was not necessary to be baptized after being baptized in other faiths, the Lord said -

"...I say unto you that all old covenants have I caused to be done away in this thing; and this is a new and an everlasting covenant..."  (Doctrine and Covenants 22:1)

For -

"...you cannot enter in at the strait gate by the law of Moses, neither by your dead works."  (Doctrine and Covenants 22:2)

"Dead" suggests meaningless, of no worth because it is of no avail. "Dead" works then include ordinances that maybe done with real intent are not valid.