agnihotraṠca darśaś ca
paurṇamÄsaÅ› ca pÅ«rva-vat
cÄturmÄsyÄni ca muner
ÄmnÄtÄni ca naigamaiḥ
agni-hotram - the fire sacrifice; ca - also; darÅ›aḥ - the sacrifice performed on the new moon day; ca - also; paurṇa-mÄsaḥ - full moon sacrifice; ca - also; pÅ«rva-vat - as previously, in the gá¹›hastha-ÄÅ›rama; cÄtuḥ-mÄsyÄni - the vows and sacrifices of cÄturmÄsya; ca - also; muneḥ - of the vÄnaprastha; ÄmnÄtÄni - enjoined; ca - also; naigamaiḥ - by expert knowers of the Vedas.
ÅšrÄ«la BhaktisiddhÄnta SarasvatÄ« ṬhÄkura has given a detailed explanation of the four rituals mentioned here, namely agnihotra, darÅ›a, paurṇamÄsa and cÄturmÄsya. The conclusion is that everyone should simply chant Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare RÄma, Hare RÄma, RÄma RÄma, Hare Hare and avoid the difficult entanglement of Vedic ritualistic ceremonies. If one neither chants Hare Kṛṣṇa nor performs such rituals, one certainly becomes a pÄá¹£aṇá¸Ä«, an atheistic fool.