putra majjanam avaha
janmarksam te ’dya bhavati
viprebhyo dehi gah sucih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Mother Yasoda further told Krsna: My dear son, because of playing all day, Your body has become covered with dust and sand. Therefore, come back, take Your bath and cleanse Yourself. Today the moon is conjoined with the auspicious star of Your birth. Therefore, be pure and give cows in charity to the brahmanas.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It is a custom of Vedic culture that whenever there is any auspicious ceremony, one should give valuable cows in charity to the brahmanas. Therefore mother Yasoda requested Krsna, “Instead of being enthusiastic in playing, now please come and be enthusiastic in charity.” Yajña-dana-tapah-karma na tyajyam karyam eva tat. As advised in Bhagavad-gita (18.5), sacrifice, charity and austerity should never be given up. Yajño danam tapas caiva pavanani manisinam: even if one is very much advanced in spiritual life, one should not give up these three duties. To observe one’s birthday ceremony, one should do something in terms of one of these three items (yajña, dana or tapah), or all of them together.