Bhagavad Gita 17.13

विधिहीनमसृष्टान्नं मन्त्रहीनमदक्षिणम् |
श्रद्धाविरहितं यज्ञं तामसं परिचक्षते

Translation

Sacrifice devoid of faith and contrary to the injunctions of the scriptures, in which no food is offered, no mantras chanted, and no donation made, is to be considered in the mode of ignorance.