Tafasta merube lo tafasta (Hebrew: תָּפַסְתָּ מְרֻבֶּה, לֹא תָּפַסְתָּ, "If you have seized a lot, you have not seized") is a Talmudic idiom used to express the idea that when it is possible to take a particular law from two different sources, it should be taken from the narrower of the two, in order to stay on the safe side and avoid making assumptions about which is correct. It is akin to the logical concept of "proving too much".