וַיִּשְׁלַ֤ח אַבְשָׁלוֹם֙ מְרַגְּלִ֔ים בְּכָל־שִׁבְטֵ֥י יִשְׂרָאֵ֖ל לֵאמֹ֑ר כְּשָׁמְעֲכֶם֙ אֶת־ק֣וֹל הַשֹּׁפָ֔ר וַאֲמַרְתֶּ֕ם מָלַ֥ךְ אַבְשָׁל֖וֹם בְּחֶבְרֽוֹן׃
But Absalom sent spies throughout all the tribes of Israel, saying: ‘As soon as ye hear the sound of the horn, then ye shall say: Absalom is king in Hebron.’
Read halakhic rulings (Jewish law) on II Samuel 15:10: and classical halakhic sources.