Bhagavad Gita · 17.13

विधिहीनमसृष्टान्नं मन्त्रहीनमदक्षिणम्।श्रद्धाविरहितं यज्ञं तामसं परिचक्षते॥

vidhi-hīnam asṛiṣhṭānnaṁ mantra-hīnam adakṣhiṇam śhraddhā-virahitaṁ yajñaṁ tāmasaṁ parichakṣhate

Sacrifice performed without regard for scriptural injunctions, without distribution of food, without mantras, without proper gifts, and devoid of faith — that is declared to be in the mode of ignorance.

— Bhagavad Gita 17.13

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)