The Pharisees had their own system of spiritual accounting that allowed them to convince themselves that they were very righteous when they were, in fact, very wicked. The Pharisees were adulterous, for Joseph Smith taught:
“The principle is as correct as the one that Jesus put forth in saying that he who seeketh a sign is an adulterous person; and that principle is eternal, undeviating, and firm as the pillars of heaven; for whenever you see a man seeking after a sign, you may set it down that he is an adulterous man.” (TPJS pg 156)
We read in the scriptures
Matthew 12:38 Then certain of the scribes and of the Pharisees answered, saying, Master, we would see a sign from thee.
39 But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas:
40 For as Jonas was three days and three nights in the whale’s belly; so shall the Son of man be three days and three nights in the heart of the earth.
Matthew 16:1 The Pharisees also with the Sadducees came, and tempting desired him that he would shew them a sign from heaven.
2 He answered and said unto them, When it is evening, ye say, It will be fair weather: for the sky is red.
3 And in the morning, It will be foul weather to day: for the sky is red and lowring. O ye hypocrites, ye can discern the face of the sky; but can ye not discern the signs of the times?
4 A wicked and adulterous generation seeketh after a sign; and there shall no sign be given unto it, but the sign of the prophet Jonas. And he left them, and departed.
The Phariees and Sadducees were adulterous. They were immoral. They are often portrayed as being very obedient, but they were very obedient to a few principles in an exaggerated way in order to convince themselves that they were very righteous. On issues like chastity and murder they were very wicked. They strained at a gnat, fretting over the least thing done on the Sabbath, while swallowing a camel, finding ways to rationalize their adulterous living and even murder.
If we will not believe Joseph Smith and Christ that the Phariesees and Sadducees were adulterous, who will we believe? What can be done for us if we will not even believe them?