Strain at a gnat?

I haven't posted here for a while, but this is a good one.
Check out Matthew 23:24 that says,  Ye blind guides, which strain at a gnat, and swallow a camel


What can that mean to strain at a gnat? You mean like looking at it really hard?


gospeldoctrine.com quotes Royal Skousen Fn, BYU Studies, vol. 26 (1986), Number 3 - Summer 1986, p. 9 which says, "“The ordinary reader must undoubtedly struggle trying to figure out what it means to ‘strain at a gnat.’ One might even guess that it means to strain one's eyes while looking at a gnat. The problem here, though, is not the word strain, but the little word at. This is a printing error that has persisted since the original 1611 publication of the King James Version. The translators intended this passage to read as follows: ‘Ye blind guides, which strain out a gnat, and swallow a camel.’ 


This confusion does not exist in Spanish. The word for strain (colar)  in Spanish does not have different meanings. It only refers to what you do when you place cheesecloth over a bottle (or use some other type of strainer) and pour something through. 


Once again, you either need to search an authority, or read it in Spanish where the meaning is much clearer.