Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 11
Sanskrit:
सन्ध्योपास्त्यादिकर्माणि वेदेनाचोदितानि मे ।पूजां तै: कल्पयेत् सम्यक् सङ्कल्प: कर्मपावनीम् ॥ ११ ॥
ITRANS:
sandhyopāstyādi-karmāṇivedenācoditāni mepūjāṁ taiḥ kalpayet samyak-saṅkalpaḥ karma-pāvanīm
Translation:
Fixing the mind on Me, one should worship Me by his various prescribed duties, such as chanting the Gāyatrī mantra at the three junctures of the day. Such performances are enjoined by the Vedas and purify the worshiper of reactions to fruitive activities.