John Lightfoot on Mark 12:42

[Two mites, which make a farthing.] Two prutahs are a farthing. "A prutah is the eighth part of an Italian assarius. An assarius is the twenty-fourth part of a silver penny." We rendered before, "The people cast money, brass," by they were casting in small money: one would think it should rather be rendered, They were casting in brass. But consider well this passage: "He that changeth the 'selaa' of the second tenth, the school of Shammai saith, Let him change the whole 'selaa' into brass." You would perhaps render it, into moneys, or into meahs, but it is properly to be rendered into brass, as appears by what follows: "The school of Hillel saith, into a shekel of silver, and a shekel of brass." So also the Glossers; and the Aruch moreover, "He that changeth a selaa, and receives for it brass money, that is, prutahs."

None might, by the canon even now mentioned, enter into the Temple, no, nor indeed into the Court of the Gentiles, with his purse, therefore much less into the Court of the Women; and yet scarce any entered who carried no money with him to be offered to the Corban, whether in his hand, or in his bosom, or elsewhere, we do not define: so did this very poor woman, who for two mites purchased herself an eternal fame, our Saviour himself setting a value upon the thing above all the gifts of them that offered.