We can get a sense of how reprehensible is a person who does not do acts of kindness from the fact that our Sages suspect such a person as being a descendant of the Mixed Multitude (Eirav Rav). For Scripture states, “He will give you mercy and be merciful to you and (Devarim 13:18); whoever has mercy on others is clearly a descendant of our Father Avraham, but whoever has no mercy for other people, is clearly not one of the descendants of our Father Avraham” (Beitza 32b). Our Sages further said, “This nation is distinguished by three characteristics: They are merciful, bashful and benevolent. Whoever does not have these three characteristics is not worthy of joining with him” (Yevamos 79b).
See how far our Sages went in describing the degradation of a person who does not do acts of kindness; they went so far as to say that “whoever denies [the importance of doing] acts of kindness, is as though he denies the existence of God.” For all these reasons, one should see to it to cling to the ways of Hashem, may He be blessed — which are nothing but goodness and kindness — and then he will have good in this World and in the World to Come.