Doctrine and Covenants 46:
7 But ye are commanded in all things to ask of God, who giveth liberally; and that which the Spirit testifies unto you even so I would that ye should do in all holiness of heart, walking uprightly before me, considering the end of your salvation, doing all things with prayer and thanksgiving, that ye may not be seduced by evil spirits, or doctrines of devils, or the commandments of men; for some are of men, and others of devils.

Doctrine and Covenants 58:
26 For behold, it is not meet that I should command in all things; for he that is compelled in all things, the same is a slothful and not a wise servant; wherefore he receiveth no reward.
27 Verily I say, men should be anxiously engaged in a good cause, and do many things of their own free will, and bring to pass much righteousness;
28 For the power is in them, wherein they are agents unto themselves. And inasmuch as men do good they shall in nowise lose their reward.
29 But he that doeth not anything until he is commanded, and receiveth a commandment with doubtful heart, and keepeth it with slothfulness, the same is damned.

2 Nephi 32:
9 But behold, I say unto you that ye must pray always, and not faint; that ye must not perform any thing unto the Lord save in the first place ye shall pray unto the Father in the name of Christ, that he will consecrate thy performance unto thee, that thy performance may be for the welfare of thy soul.