SB 10.43.1
sri-suka uvaca
atha krsnas ca ramas ca
krta-saucau parantapa
malla-dundubhi-nirghosam
srutva drastum upeyatuh
Translation:
Sukadeva Gosvami said: O chastiser of enemies, Krsna and Balarama, having executed all necessary purification, then heard the kettledrums resounding at the wrestling arena, and They went there to see what was happening.
Purport:
Srila Sridhara Svami explains the words krta-saucau, “having executed all necessary purification,” as follows: “Two days previously, Krsna and Balarama had executed Their purification, Their relief from offense [by performing heroic deeds]. The Lords reasoned: ‘Even after We have made Our power known by breaking the bow and by performing other feats, Our parents have still not secured freedom. Kamsa is again trying to kill them. Therefore, although he is Our maternal uncle, it will not be wrong for Us to kill him.’ They assured Their offenselessness by this reasoning.”