John Gill Commentary Mark 12:44

"for they all did cast in of their superfluity; but she of her want did cast in all that she had, [even] all her living." — Mark 12:44 (ASV)

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.