DEUT651 And it states (Shabbos 151b): "'That he may grant you mercy and be merciful to you' [this verse] means that Heaven is merciful to all who have mercy on their fellow creatures." This is self-evident, for the Holy One blessed be He operates with the principle of "measure for measure," and one who is merciful and benevolent toward his fellow creatures will, when he is judged, be judged with mercy, and all of his sins will be benevolently forgiven. This exoneration shows an exact justice since "measure for measure" has determined it. This is what our Sages of blessed memory have said (Rosh Hashanah 17a): "Whose transgression does He [the Eternal] pardon? That of the one who overlooks [the] sin [that another client has committed against him]." If one is unwilling to make concessions in his own demands or is unwilling to act with kindness, reason dictates that he too should be treated with [the same] measure of exactitude. But can you imagine that there is a person [ alive] who would be able to withstand being judged by the Holy One blessed be He according to the measure of exactitude?! David HaMelech prayed when he said (Tehillim 143:2): "And do not enter into judgment with Your servant, for no living being can find justification before You." Simultaneously, he who engages in chesed will receive chesed [in return], and the more he engages in it the more he will receive. David was able to exult in the possession of this excellent virtue – he would even try to be benevolent toward those who hated him. This is what he referred to when he said (ibid. 35:13): "And I, when they were ill, closed myself in sackcloth, I afflicted my soul with fasting.…" And he said (ibid.7:5): "If I have repaid with evil those who were at peace with me.…" The virtue of piety also requires that one should not cause any creature to suffer, even animals, and show mercy and compassion toward them. Similarly, it says (Mishlei 12:10): "The righteous man knows the soul of his beast." And there are those who are of the opinion that "causing an animal to suffer as a prohibition of the Torah (Shabbos 128b)." And at the very least it is a Rabbinic enactment. In summary: Compassion and benevolence must be permanently ingrained in the heart of the pious, and one's objective should always be to please his fellow creatures and not to cause them any suffering, etc.