Deuteronomy 13:15

ודרשת וחקרת ושאלת היטב THEN SHALT THOU INQUIRE, AND MAKE SEARCH, AND ASK DILIGENTLY — From here — from the variety of expressions denoting inquiry in this verse — they (the Rabbis) derived the law of investigating capital cases by means of seven investigations” (referring to date, time and place). in the following manner: here (in our verse) there occur three expressions relating to inquiry, viz., ודרשת, וחקרת and היטב — the expression ושאלת does not come into account, because from it they derived בדיקות, the examination referring to accompanying circumstances, — and in another passage (Deuteronomy 19:18) it states, “and the judges shall enquire diligently (ודרשו השופטים היטב)”, and still in another passage (Deuteronomy 17:40) it states, “and thou shalt inquire diligently (ודרשת היטב)" — thus altogether seven expressions. — And although they are used in connection with different cases they learned by way of analogy (ג"ש) of the term היטב used here and in the passages quoted that it is intended to apply what is stated in one case to the others also (Sanhedrin 40a; cf. Sifrei Devarim 93:6).

וְדָרַשְׁתָּ֧ וְחָקַרְתָּ֛ וְשָׁאַלְתָּ֖ הֵיטֵ֑ב וְהִנֵּ֤ה אֱמֶת֙ נָכ֣וֹן הַדָּבָ֔ר נֶעֶשְׂתָ֛ה הַתּוֹעֵבָ֥ה הַזֹּ֖את בְּקִרְבֶּֽךָ׃

then shalt thou inquire, and make search, and ask diligently; and, behold, if it be truth, and the thing certain, that such abomination was done among you;