Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 22
Sanskrit:
पाद्यार्घ्याचमनीयार्थं त्रीणि पात्राणि देशिक: ।हृदा शीर्ष्णाथ शिखया गायत्र्या चाभिमन्त्रयेत् ॥ २२ ॥
ITRANS:
pādyārghyācamanīyārthaṁtrīṇi pātrāṇi deśikaḥhṛdā śīrṣṇātha śikhayāgāyatryā cābhimantrayet
Translation:
The worshiper should then purify those three vessels. He should sanctify the vessel holding water for washing the Lord’s feet by chanting hṛdayāya namaḥ, the vessel containing water for arghya by chanting śirase svāhā, and the vessel containing water for washing the Lord’s mouth by chanting śikhāyai vaṣaṭ. Also, the Gāyatrī mantra should be chanted for all three vessels.