O Kaṁsa, you fool, what will be the use of killing me? The Supreme Personality of Godhead, who has been your enemy from the very beginning and who will certainly kill you, has already taken His birth somewhere else. Therefore, do not unnecessarily kill other children.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
किं मया हतया मन्द जातः खलु तवान्तकृत् । यत्र क्व वा पूर्वशत्रुर्मा हिंसीः कृपणान् वृथा
kiṃ mayā hatayā manda jātaḥ khalu tavāntakṛt | yatra kva vā pūrvaśatrurmā hiṃsīḥ kṛpaṇān vṛthā
SB 10.4.12