Todalatantra 4.2

4.2

īśvara uvāca
śṛṇu cārvaṅgi subhage tārāyāḥ pūjanaṃ mahat
mantreṇācamanaṃ kṛtvā gurudevaṃ namettataḥ //

The Lord said: / Hear, O fair-limbed, fortunate one, the great worship of Tārā: / having sipped water with the mantra, one should then bow to the guru.