There are a number of accounts in the scriptures where God appears to support deception under certain circumstances. This seems to conflict with the generally accepted understanding that God would never deceive anyone nor would He encourage someone else to do it. I'll review some relevant scriptures and then propose a solution to this apparent conflict.
First we should show the definition of deceive:
to mislead by a false appearance or statement
"deceive." Dictionary.com Unabridged. Random House, Inc. 27 Dec. 2011. <Dictionary.com http://dictionary.reference.com/browse/deceive>.
In Genesis 22 we read the following:
1 And it came to pass after these things, that God did tempt Abraham, and said unto him, Abraham: and he said, Behold, here Iam.
2 And he said, Take now thy son, thine only son Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of.
This passage seems to suggest that God made Abraham believe that he would need to kill his son. That seems like deception.
In the Pearl of Great Price, Abraham Chapter 2 we read:
22 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;
23 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:
24 Let her say unto the Egyptians, she is thy sister, and thy soul shall live.
In this account, the Lord tells Abraham to deceive the Egyptians.
The scriptures make it very clear how God feels about deception:
Lying lips are abomination to the Lord, Prov. 12:22
So what is the explanation for this conflict?
I don't believe God would ever deceive someone or to encourage anyone else to deceive. To always speak the truth is such a foundation principle I don't see how deception could be justified. Because He always speaks the truth we can have complete confidence in Him; we couldn't have that same confidence if He might mislead us even for a good cause.
My conclusion is that the scriptures are incorrect. They could have been translated or transcribed incorrectly. Another possibility is false revelation.
So who told Abraham to sacrifice Isaac? I suspect it was actually a false revelation from a source other than God. The nature of revelation is such that it's difficult to know with certainty the source of a revelation. Even good people can fall victim to false revelation, making it very important to use wisdom in discerning truth.
In the case of Abraham and Sarai in Egypt, I suspect it was Abraham who decided that deception was appropriate and not God.