Two mites - The word translated "mite" denotes a small coin made of brass - the smallest in use among the Jews. The precise value cannot now be easily estimated. It was much less than any coin we have, as the "farthing" was less than an English farthing. It was in value about three mills and a half, or one-third of a cent.

And there came a certain poor widow,.... Among the many that came to offer their gifts freely, there came one that was particularly taken notice of by Christ; and she was a "widow", had no husband to provide for her, and was a "poor" one; had no substance left her by her husband to support her with; very likely she was an inhabitant of Jerusalem:
and she threw in two mites, which make a farthing; a "quadrant", which was the fourth part of the Roman assis, or farthing; which seems to be much the same with the of the Greeks, which is said (g) to be,
"the fourth part of an obolus (the least Athenian coin), that is, two brass pieces.''
These mites seem to be the same with the "prutas", the Jews often speak of; who say (h), that a "pruta" is the eighth part of an Italian farthing; though some make it to be the sixth: hence the Syriac version here renders it, "two menin, that is, eighths"; and the Jerusalem Talmud expressly says (i), that, , "two prutas make a quadrant", the very word here used: and that the Jews took the freewill offerings of the poor as well as the rich, though ever so little, is clear from this canon of theirs (k);
"a poor man that gives a "pruta", or mite, into the alms dish, or a "pruta" into the poor's chest, they take it of him; but if he does not give, they do not oblige him to give.''
Nor were they obliged to cast into the treasury; but if they did, they received it, be it less or more: and indeed, the rich might throw in as little as they pleased: as for instance; into the chest for gold, they might throw in as little as the weight of a barley corn of gold; and into the chest for frankincense, as little as the weight of a barley corn of frankincense (l). The Persic version here, different from all others, instead of "two mites", renders it, "two bottoms of thread", or "yarn".
(g) Harpocratian. Lexic. p. 281. (h) Misn. Kiddushin, c. 1. sect. 1. T. Hieros. Kiddushin, fol. 58. 4. T. Bab. Kiddushin, fol. 12. 1. Bava Metzin, fol. 44. 2. Maimon. Hilch. Shekalim, c. 1. sect. 3. (i) Kiddushi, fol. 58. 4. (k) Maimon. Hilch. Mattanot Anayim, c. 9. sect. 19. (l) Maimon. & Battenora in. Misn. Shekalim, c. 6. sect. 6.

There came a certain poor widow. Here, as in other places in the Bible, we must remember the exceedingly depressed and dependent condition of a poor man's widow in the countries where our Lord was. The expression is almost proverbial for one very badly off, and most unlikely to contribute anything to a charitable purpose.
Two mites. The smallest of Jewish coins, about the value of one-fifth of a cent. It took its name from its extreme smallness, being derived from an adjective signifying thin.
A farthing. Mark (not Luke) adds for his Roman readers an explanation, using a Greek word (taken from the Latin), meaning the fourth part, as our word "farthing" does. The value is only of importance as showing upon how minute a gift our Lord pronounced this splendid panegyric, which might be envied by a Croesus or a Rothschild.