One verse

Srimad Bhagavatam 7.12.2

7.12.2

सायं प्रातरुपासीत गुर्वग्‍न्यर्कसुरोत्तमान् । सन्ध्ये उभे च यतवाग्जपन्ब्रह्म समाहित: ॥ २ ॥

sayam pratar upasita gurv-agny-arka-surottaman sandhye ubhe ca yata-vag japan brahma samahitah

sayam
in the evening
pratah
in the morning
upasita
he should worship
guru
the spiritual master
agni
the fire (by a fire sacrifice)
arka
the sun
sura-uttaman
and Lord Visnu, Purusottama, the best of personalities
sandhye
morning and evening
ubhe
both
ca
also
yata-vak
without talking, being silent
japan
murmuring
brahma
the Gayatri mantra
samahitah
being fully absorbed.

At both junctions of day and night, namely, in the early morning and in the evening, he should be fully absorbed in thoughts of the spiritual master, fire, the sun-god and Lord Visnu and by chanting the Gayatri mantra he should worship them.