Bat in Fausset's Bible Dictionary

(hatalleph; "the darkness bird".) Delighting in dark holes and caverns. This is the point of Isaiah 2:20, "a man shall cast his idols to the bats," while the idolaters themselves shall vainly hide in the rock from the wrath of the Lamb (Revelation 6:16). Unclean in the eye of the law (Deuteronomy 14:18-19; Leviticus 11:19-20). Ranked among "all fowls that creep, going upon all four;" it has claws on its pinions, by which it attaches itself to a surface, and creeps along it. It is connected with quadrupeds: the bones of the arm (answering to a bird's wing) and fingers being elongated, and a membrane extended over them to the hind limbs.