Deaf as an adder proverbial expression meaning very deaf, probably originally with biblical allusion to the ‘deaf adder that stoppeth her ear’ of Psalm 58:4–5, ‘Which will not hearken to the voice of charmers: charming never so wisely.’
a deaf husband and a blind wife are always a happy couple proverbial saying, late 16th century, meaning that each will remain unaware of drawbacks in the other. The saying is sometimes reversed to a blind husband and a deaf wife.
there's none so deaf as those who will not hear proverbial saying, mid 16th century, used to refer to someone who chooses not to listen to unwelcome information. (Compare there's none so blind as those who will not see.)