In Talmudical hermeneutics, asmachta is a hint found in the Hebrew Bible for rabbinical prohibitions or any other Halakha. It's an exception in the talmudical hermeneutics, since it doesn't base the law on the cited verse, but uses the verse as a hint.
Contents
Sometimes it isn't clear whether the verse has been quoted as an asmachta or as a source, what might lead to a controversy over the de'oraita or derabanan quality of the law. An example for such case is the controversy over the quality of Berakhah levatala - the prohibition to say a prayer outside its context. The Talmud says whoever says unneeded Berakhah violates the verse Thou shalt not take the name of the Lord thy God in vain. While Maimonides sees it as a source, Tosafot sees it as an asmachta.
Examples
Meaning
According to Maimonides, this is only a mark the sages gave for memory. Kuzari says a similar thing.
Yom Tov Asevilli objects to Maimonides' explanation, and claims God himself thought of the asmachta commentary, and hid it as a hint to be used by the sages. "Every law with a biblical 'asmachta', God witnessed it as recommended, but haven't ruled it as obligatory, and left it for sages' decision. And this way is surely truth, and not the way of some commentrators, saying it is only sages' sign and torah haven't meant it. God forbid, this notion shouldn't be said, it is heresy."