The Book of Abraham clarifies the following Biblical event to include a circumstance where God would justify lying:

“And it came to pass when I was come near to enter into Egypt, the Lord said unto me: Behold, Sarai, thy wife, is a very fair woman to look upon; Therefore it shall come to pass, when the Egyptians shall see her, they will say—She is his wife; and they will kill you, but they will save her alive; therefore see that ye do on this wise: Let her say unto the Egyptians, she is thy sister, and thy soul shall live. And it came to pass that I, Abraham, told Sarai, my wife, all that the Lord had said unto me—Therefore say unto them, I pray thee, thou art my sister, that it may be well with me for thy sake, and my soul shall live because of thee.”

Joseph Smith, Jr., Pearl of Great Price (Salt Lake City, UT: The Church of Jesus Christ of Latter-day Saints, 1977 green leather edition), The Book of Abraham 2:22-25, page 33.