D&C 124

The Lord said - 

"...let my servant John C. Bennett help you in your labor in sending my word to the kings and people of the earth, and stand by you, even you my servant Joseph Smith, in the hour of affliction; and his reward shall not fail if he receive counsel.

17 And for his love he shall be great, for he shall be mine if he do this, saith the Lord. I have seen the work which he hath done, which I accept if he continue, and will crown him with blessings and great glory."  (Doctrine and Covenants 124:16–17)

Again, the Lord warns with an "if".  John C. Bennett eventually apostatized and became an ardent enemy of the Church.  One might ask why the Lord would give such an important calling knowing what would happen?  John Taylor answered - 

“Respecting John C. Bennett: I was well acquainted with him. At one time he was a good man, but fell into adultery, and was cut off from the Church for his iniquity” (History of the Church, Vol. V, p. 81).

A warning to us all!