Of their abundance - Of their superfluous store. They have given what they did not "need." They could afford it as well as not, and in doing it they have shown no self-denial.
She of her want - Of her poverty.
All her living - All that she had to live on. She trusted in God to supply her wants, and devoted her little property entirely to him. From this passage we may learn:
1. That God is pleased with offerings made to him and his cause.
2. That it is our duty to devote our property to God. We received it from him, and we shall not employ it in a proper manner unless we feel that we are stewards, and ask of him what we shall do with it. Jesus approved the conduct of all who had given money to the treasury.
3. That the highest evidence of love to the cause of religion is not the "amount" given, but the amount compared with our means.
4. That it "may be" proper to give "all" our property to God, and to depend on his providence for the supply of our wants.
5. That God does not despise the humblest offering, if made in sincerity. He loves a cheerful giver.
6. That there are none who may not in this way show their love to the cause of religion. There are few, very few students in Sunday Schools who may not give as much to the cause of religion as this poor widow; and Jesus would be as ready to approve their offerings as he was hers: and the time to "begin" to be benevolent and to do good is in early life, in childhood.
7. That it is every man's duty to inquire, not how much he gives, but how much compared with what he has; how much self-denial he practices, and what is the "motive" with which it is done.
8. We may remark that few practice self-denial for the purpose of charity. Most give of their abundance - that is, what they can spare without feeling it, and many feel that this is the same as throwing it away. Among all the thousands who give to these objects, how few deny themselves of one comfort, even the least, that they may advance the kingdom of Christ!

For all they did cast in of their abundance,.... Or "superabundance", as the Arabic version renders it; or "superfluity", as the Ethiopic: they abounded in the things of the world, of which they gave only a part; and though they might give much, yet they could easily spare it, and had enough remaining:
but she, of her want; or "penury", as in Luke 21:4; see 2-Corinthians 8:2;
did cast in all that she had, even all her living; her whole substance, all that she had in the world; what was to have bought her food, for that day; she left herself nothing, but gave away all, and trusted to providence for immediate supply.

For. The worth of a gift is to be determined, not by intrinsic value, but by what it costs the giver. The measure of that cost is what is left, not what is given. For the widow to give her mites was noble; for one well off to give "his mite" is contemptible.
All that she had, all her living. Out of her want, out of her destitution, she has cast in all that (in cash) she possessed--her whole (present) means of subsistence. In love she devoted all of God, with strong faith in his providential care.