supuṇyaṁ vyatanod yaśaḥ
kalau — in this Age of Kali; janiṣyamāṇānām — of the conditioned souls who will take birth in the future; duḥkha-śoka-tamaḥ-nudam — to minimize their unlimited unhappiness and lamentation, which are caused by ignorance; anugrahāya — just to show mercy; bhaktānām — to the devotees; su-puṇyam — very pious, transcendental activities; vyatanot — expanded; yaśaḥ — His glories or reputation.
To show causeless mercy to the devotees who would take birth in the future in this Age of Kali, the Supreme Personality of Godhead, Kṛṣṇa, 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 Kṛṣṇa consciousness stated in Bhagavad-gītā, could be relieved from the pangs of material existence.]
The Lord’s activities of saving the devotees and killing the demons (paritrāṇāya sādhūnāṁ vināśāya ca duṣkṛtām) take place side by side. Kṛṣṇa actually appears for the deliverance of the sādhus, or bhaktas, but by killing the demons He shows them mercy also, for anyone killed by Kṛṣṇa is liberated. Whether the Lord kills or gives protection, He is kind to both the demons and the devotees.