Our Lord alludes here to the gnat in a proverbial expression probably in common use, “who strain out the gnat;” the words in the King James Version, “strain at a gnat,” being a mere typographical error, which has been corrected in the Revised King James Version.
The custom of filtering wine for this purpose was common among the Jews. It was founded on Lev. 11:23. It is supposed that the “lice,” Ex. 8:16 (marginal note Revised King James Version, “sand-flies”), were a species of gnat.