vidhi-disto ya ijyate
yastavyam eveti manah
samadhaya sa sattvikah
Of sacrifices, the sacrifice performed according to the directions of scripture, as a matter of duty, by those who desire no reward, is of the nature of goodness.
Commentary by Srila Prabhupada
The general tendency is to offer sacrifice with some purpose in mind, but here it is stated that sacrifice should be performed without any such desire. It should be done as a matter of duty. Take, for example, the performance of rituals in temples or in churches. Generally they are performed with the purpose of material benefit, but that is not in the mode of goodness. One should go to a temple or church as a matter of duty, offer respect to the Supreme Personality of Godhead and offer flowers and eatables. Everyone thinks that there is no use in going to the temple just to worship God. But worship for economic benefit is not recommended in the scriptural injunctions. One should go simply to offer respect to the Deity. That will place one in the mode of goodness. It is the duty of every civilized man to obey the injunctions of the scriptures and offer respect to the Supreme Personality of Godhead.
Commentary by Sri Visvanatha Cakravarti Thakur
With this verse the Lord begins to speak of the three types of sacrifice. That is sattvika sacrifice which is performed according to the rules with no desire for results. What would be the impetus for sacrifice if there were no desire for results? The mind is fixed in performing the sacrifice with the idea that it should be done because the scriptures prescribe it thus (yastavyam eva iti).