″Whoso diggeth a pit shall fall therein: and he that rolleth a stone, it will return upon him. A lying tongue hateth those that are afflicted by it; and a flattering mouth worketh ruin. ″
(Proverbs 26:27-28 KJV)

Proverbs 26:27
Whoso diggeth a pit shall fall therein,…. That devises mischief against others, it shall come upon himself. The allusion is to the digging of pits for catching wild beasts, which are slightly covered with earth; and which sometimes the pursuers, through inadvertency, fall into themselves; the passage seems to be taken from Psa_7:15;

and he that rolleth a stone, it will return upon him; that rolls a stone up hill, if he does not take care, it will return back, and fall with great force upon himself; so the mischief which a wicked man labours hard at, as men do in digging a pit, or rolling a stone, in time rolls back upon themselves; the measure they mete out to others is measured to them. Jarchi makes mention of an “hagadah”, or exposition, which illustrates this passage, by the case of Abimelech; who slew threescore and ten persons on one stone, and was himself killed with a piece of a millstone cast upon him, Jdg_9:18; this may put in mind of the fable of Sisyphus (o), feigned in hell to roll a great stone to the top of a mountain, which presently falling down on his head, made his labour fruitless.

Proverbs 26:28
A lying tongue hateth those that are afflicted by it,…. That is, a man of a lying tongue, that is given to lying, hates those that are hurt and crushed by his lies; the reason why he hurts them with his lies is because he hates them; and, having hurt them, he hates them, being made his enemies, and from whom he may expect and be in fear of revenge: moreover, he hates those that are troubled at and disturbed with his lies; or the “contrite” (p) and humble men: or those who “smite” or “strike” (q) him, as some render the word, actively; that is, reprove him, and bring him to shame for lying. The words are by some translated, a “contrite” person, or everyone of “the contrite ones, hateth a lying tongue” (r); such as are of a broken and of a contrite spirit, and that tremble at the word of God, or are hurt by lies, these abhor a liar. The Targum is,

“a lying tongue bates the ways of truth;”

and the Septuagint, Syriac, and Arabic versions, render it, “a lying tongue hate truth”; and so the Vulgate Latin version, “a lying tongue loves not truth”; for nothing is more contrary to a lie than truth;

and a flattering mouth worketh ruin; both to itself and to the persons flattered by it: or, “makes an impulse” (s); a pushing, a driving away; it drives away such as cannot bear its flatteries: and pushes on such that are taken with it, both into sin and into ruin.

John Gill – Bible commentaries 

Read the whole of Proverbs 26,  some wonderful exhortations for the believer.