supunyam vyatanod yasah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
To show causeless mercy to the devotees who would take birth in the future in this Age of Kali, the Supreme Personality of Godhead, Krsna, acted in such a way that simply by remembering Him one will be freed from all the lamentation and unhappiness of material existence. [In other words, He acted so that all future devotees, by accepting the instructions of Krsna consciousness stated in Bhagavad-gita, could be relieved from the pangs of material existence.]
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Lord’s activities of saving the devotees and killing the demons (paritranaya sadhunam vinasaya ca duskrtam) take place side by side. Krsna actually appears for the deliverance of the sadhus, or bhaktas, but by killing the demons He shows them mercy also, for anyone killed by Krsna is liberated. Whether the Lord kills or gives protection, He is kind to both the demons and the devotees.