The gemara (Bava Basra 10a) relates that the Roman general Turnus-Rufus asked the Talmudic sage Rabbi Akiva, "If, as you claim, your G-d loves the poor, why doesn't He support them?" Rabbi Akiva answered, "He is giving the rest of us the opportunity to avoid the judgement of gehinom - purgatory, by supporting the poor."

     Turnus-Rufus retorted, "To the contrary, for this you truly deserve punishment. If a king imprisons his servant and starves him, and another servant sneaks in and feeds him, does the latter not incur the death penalty? Since you are called 'servants' as the scripture states, 'To Me, the children of Israel are servants,' how can you do this?" 

     "That is the wrong analogy," Rabbi Akiva replied. "If a king imprisons his own son and starves him, and a servant sneaks in and feeds the king's son, does the latter not earn a great reward from the king? And furthermore, we are called 'children' of Hashem, as it is written, ''בנים אתם לה - 'You are children to Hashem'."

     Explains the great Gaon, R' Akiva Eiger zt"l, this is what our posuk means: "השמר לך פן יהיה דבר עם לבבך בליעל" - "Beware lest there be a lawless thought in your heart." Do not maintain that the poor do not deserve to be supported through our charity, because this is lawless and untrue. As a result, if you do that, "והיה בך חטא" - "it will be a sin against you" - you will not only forfeit the mitzvah of tzedakah, but you will be convicting yourself as well, for you will be suggesting that we are not to be perceived as Hashem's children, but only as His servants, and as such, we feel no responsibility to assist our brethren in need.