rāma rāma - my dear son Paraśurāma; mahābāho - O great hero; bhavān - you; pāpam - sinful activities; akāraṣīt - have executed; avadhīt - have killed; naradevam - the king; yat - who is; sarva-deva-mayam - the embodiment of all the demigods; vṛthā - unnecessarily.

O great hero, my dear son Paraśurāma, you have unnecessarily killed the king, who is supposed to be the embodiment of all the demigods. Thus you have committed a sin.