You (Hindus) read and recite Gyatri2 and other Mantras for the praise and greatness of gods and do Sandhya (worship) through Angan Yas3 (touching various parts of the body) and you offer water to gods and your ancestors but such worship is forbidden in Sikh religion. Only contemplation of God, meditation of All Pervading Power, through Gurbani is recommended.
ਏਹਾ ਸੰਧਿਆ ਪਰਵਾਣੁ ਹੈ ਜਿਤੁ ਹਰਿ ਪ੍ਰਭੁ ਮੇਰਾ ਚਿਤਿ ਆਵੈ ॥ ਹਰਿ ਸਿਉ ਪ੍ਰੀਤਿ ਊਪਜੈ ਮਾਇਆ ਮੋਹੁ ਜਲਾਵੈ ॥ ਗੁਰ ਪਰਸਾਦੀ ਦੁਬਿਧਾ ਮਰੈ ਮਨੂਆ ਅਸਥਿਰੁ ਸੰਧਿਆ ਕਰੇ ਵੀਚਾਰੁ ॥ ਨਾਨਕ ਸੰਧਿਆ ਕਰੈ ਮਨਮੁਖੀ ਜੀਉ ਨ ਟਿਕੈ ਮਰਿ ਜੰਮੈ ਹੋਇ ਖੁਆਰੁ ॥1॥
That evening prayer alone is acceptable, which brings the Lord God to my consciousness. Love for the Lord wells up within me, and my attachment to Maya is burnt away. By Guru's Grace, duality is conquered, and the mind becomes stable; I have made contemplative meditation my evening prayer. O Nanak, the self-willed manmukh may recite his evening prayers, but his mind is not centered on it; through birth and death, he is ruined. ||1|| (Guru Granth Sahib Ji, Ang 553)
ਸੰਧਿਆ ਤਰਪਣੁ ਕਰਹਿ ਗਾਇਤ੍ਰੀ ਬਿਨੁ ਬੂਝੇ ਦੁਖੁ ਪਾਇਆ ॥2॥
He says his evening prayers, and makes offerings of water, and recites his morning prayers, but without true understanding4, he still suffers in pain. ||2|| (Guru Granth Sahib Ji, Ang 603)
The daily routine that is recommended to the Sikhs is stated by Bhai Gurdas Ji as follows:
ਅੰਮ੍ਰਿਤ ਵੇਲੈ ਨਾਵਣਾ ਗੁਰਮੁਖਿ ਜਪੁ ਗੁਰ ਪੰਤੁ ਜਪਾਇਆ । ਰਾਤਿ ਆਰਤੀ ਸੋਹਿਲਾ ਮਾਇਆ ਵਿਚਿ ਉਦਾਸੁ ਰਹਾਇਆ ।
Take bath in the early hours and meditate on the Mantra of the Guru. At night perform the Arti of Sohla (hymns of His praise) and stay unattached surrounded by Maya. (Bhai Gurdas Ji, Vaar 26)
Bhai Daya Singh has stated in his Rehat Nama:
ਗੁਰੂ ਕਾ ਸਿੱਖ ਤਰਪਣ ਗਾਯਤ੍ਰੀ ਵਲ ਚਿਤ ਨ ਦੇਵੇ ।
A Sikh of the Guru should not pay attention to Tarpan ad Gyatri.
1) To read mantras while touching heart, arms, eyes etc. and to clap.
2) ਤਤ ਸਵਿਤੁ: ਵਰੇਣਯੰ ਭਰਗੋ ਦੇਵਸਯ ਧੀ ਮਹਿ, ਧਿਯੋ ਯੋਨ: ਪ੍ਰਚੋਦਯਾਤ ।
This is the gyatri mantra and it is basic to Hindu Dharma. In the beginning of this Mantra Hindu Rishis have added ਓਅੰ ਭੂ: ਭੁਵ:ਸ੍ਵ:. It means “the sun god that makes possible all life frees us from all difficulties and maladies. It is evident one can address one’s prayer to it. It destroys our sins and directs our senses. We contemplate and fix our attention on it.” These days many Hindu scholars interpret Gyatri in respect of God but in fact it is in praise of the sun. Vishvamittar is the author of the Gyatri.
3) To read mantras after touching heart, arms, eyes etc. and to clap.
4) Without understanding that the Primal God is the support of all, and forgetting Him means everything is worthless. In other words, only worshipping One God is fruitful.