Verses 24-25 - Cunning people often practice guile; pretending to be friendly to those they hate in order to find a way to hurt them. There are many Biblical accounts of such deceit. It is probable that Abel's murder is one of those, for Cain, after becoming angry, "...talked to Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him" (Genesis 4:8). Genesis 34 records the deceit enacted by Jacob's sons, who in vengeance for their sister Dinah, feigned friendship with Shechem and his family, so that they could easily kill them.
We ought to be cautious in making new friends and should certainly beware if anyone who has previously hated us suddenly becomes friendly. Verse 25 says that there are seven abominations in the heart of one who poses as a friend. These abominations may be the ones listed in Proverbs 6:16-19: "These six things doth the LORD hate: yea, seven are an abomination unto him: A proud look, a lying tongue, and hands that shed innocent blood, An heart that deviseth wicked imaginations, feet that be swift in running to mischief, A false witness that speaketh lies, and he that soweth discord among brethren."
We will recall that Jesus said that he who hates anyone commits murder in his heart, and that he who looks at a woman with lust commits adultery in his heart. In the same way, these seven sins can be present in the hearts of those who pretend friendship. We should be careful to befriend only those of proven good character. This does not mean we are to shun people in the world, as we should witness to them through our godly actions, but we should not make friends with sinners.
Verse 26 - A cunning person may successfully conceal his hatred, but regardless of how many people he deceives, his wickedness will eventually be exposed. There may be a public exposure on earth or exposure before the church on Judgment Day, when Christ separates those who think themselves to be Christians from those who really are (Matthew 7:21-23). Sooner or later, sins concealed by guile will be revealed. "...Ye have sinned against the LORD: and be sure your sin will find you out" (Numbers 32:23b).