Sefer Imrei Noam explains this verse by citing the Gemara (Pesachim 8B) that states: “If one gives a coin to tzedakah so that his son should be healed, he is a complete tzadik.” We see from this that although one does not receive reward for most mitzvos in this world, the mitzvah of tzedakah is an exception. If one gives tzedakah, he is rewarded in this world as well. Even if one gives tzedakah with a personal agenda – such as so that his son should be healed from an illness – he is considered a complete tzadik and he will be rewarded by being granted his request.
This is also seen from the pasuk (Mishlei 11:24): “Yesh mefazer v’nosef od.” (There is one who gives away his money to charity and his worth increases because he is rewarded.) Thus, one who gives tzedakah can be called by the name “Od Yosef”, which can be translated to mean that his net worth increases as the more one gives to tzedakah, the more reward he will receive in this world.
Accordingly, this pasuk can be understood to be saying: “Rav od Yosef” – the power of tzedakah is great (rav). “I will go and see him before he dies” – even if one gives charity in order to prevent the death of his son, the power is still great and the mitzvah will bear reward.
רַ ב עוֹד יוֹסֵף בְּנִי חָי אֵלְכָה וְאֶרְ אֶנּוּ בְּטֶרֶ ם אָמוּת (מה, כח)
It is enough. My son Yosef is still alive. I will go and see him before I die. (45:28)
