Chapter 17, Verse 13
Part of 17: Śhraddhā Traya Vibhāg Yog — श्रद्धात्रयविभागयोगविधिहीनमसृष्टान्नं मन्त्रहीनमदक्षिणम्।श्रद्धाविरहितं यज्ञं तामसं परिचक्षते॥
vidhi-hīnam asṛiṣhṭānnaṁ mantra-hīnam adakṣhiṇam śhraddhā-virahitaṁ yajñaṁ tāmasaṁ parichakṣhate
They declare that sacrifice to be Tamasic which is contrary to the ordinances of the scriptures, in which no food is distributed, and which is devoid of mantras, gifts, and faith.
A sacrifice performed by a Tamasic man is never guided by any consideration for the prescribed rites or incantation. You will find every irregularity in this sacrifice. No food is distributed. No fees which are prescribed in the scriptures are given to the priests. The Mantras are not changed properly. The hymns recited are defective in utterance and accent. Sometimes there is no recitation at all. There is no faith. A man who performs such a sacrifice does not get any merit.