The various types of offerings brought on the altar in the Sanctuary and in Jerusalem were classified as Major Sanctity and Lesser Sanctity. The Mincha (meal) offering of the poor is called Kodesh Kodoshim (Major Sanctity) "like the sin-offering" of the repentant.
Abarbanel, the great Spanish commentator, observes that while other offerings may be of relatively minor sacredness, those of the poor, who give with sacrifice and self-denial, are of major holiness. Similarly, the expression of contrition by the erstwhile sinner, his remorse for evildoing, is cherished by his merciful Creator.
The significance of the offering lies less in its quantitative measure than in the degree that the donor is involved, how much of himself he offers. The wealthy with their more lavish philanthropies need not patronize their less grandly endowed brothers. At the same time, the measure for G-d being the heart, it ill becomes the modest contributor to charity to deprecate the wealthy or to boast of his own relative generosity ("if I can give five dollars he can give ten thousand..."). While the negotiable value of the large gifts of the wealthy is not diminished by pride, small charities given arrogantly have little material or spiritual significance.