Origen

Mark how the righteous dwell upon each word, while the unrighteous answer summarily, and not going through the particular instances; for so it becomes the righteous out of humility to disclaim each individual generous action, when imputed to them publicly; whereas bad men excuse their sins, and endeavour to prove them few and venial. And Christ’s answer conveys this. And to the righteous He says, In that ye did it to my brethren, to shew the greatness of their good deeds; to the sinners He says only, to one of the least of these, not aggravating their sin. For they are truly His brethren who are perfect; and a deed of mercy shewn to the more holy is more acceptable to God than one shewn to the less holy; and the sin of overlooking the less holy is less than of overlooking the more holy.