Hazrat Abu Ja’far Balkhi (rahimahullah) mentioned the following:

I heard that if Imaam Abu Hanifah (rahimahullah) encountered difficulty in understanding any mas’alah and found the mas’alah to be complex and confusing, then he would address his students and say, “This difficulty can only be on account of a sin that I must have committed.” Imaam Abu Hanifah (rahimahullah) would thus engage in istighfaar (repenting to Allah Ta‘ala). Sometimes, Imaam Abu Hanifah (rahimahullah) would stand, make wudhu, perform two rakaats of salaah and thereafter repent to Allah Ta‘ala.