וְדָוִד֙ הִגִּ֣יד לֵאמֹ֔ר אֲחִיתֹ֥פֶל בַּקֹּשְׁרִ֖ים עִם־אַבְשָׁל֑וֹם וַיֹּ֣אמֶר דָּוִ֔ד סַכֶּל־נָ֛א אֶת־עֲצַ֥ת אֲחִיתֹ֖פֶל יְהוָֽה׃
And one told David, saying: ‘Ahithophel is among the conspirators with Absalom.’ And David said: ‘O LORD, I pray Thee, turn the counsel of Ahithophel into foolishness.’
Read halakhic rulings (Jewish law) on II Samuel 15:31: and classical halakhic sources.