What is Yagnopavit Sanskar
It is the formal ceremony to consecrate the sacred thread, signifying the initiation into sacred scripture study of the youth and formally handing a youth to a spiritual teacher.
गृह्योक्तकर्मणा येन समीपं नीयते गुरोः । बालो वेदाय तद्योगात् बालस्योपनयं विदुः
(Gṛhyoktakarmaṇā yena samīpaṃ nīyate guroḥ | bālo vedāya tadhyogāt bālasyopanayaṃ viduḥu) ||
(Spiritual birth is conferred upon the youth, and he becomes a Dvij (the twice born))
(Manusmṛti 2.36-38)
गर्भाष्टमे ब्राह्मण उपनेय इत्युपनयनं संस्कारार्थम्
(Garbhāṣṭame brāhmaṇa upaneya ityupanayanaṃ saṃskārārtham) Mahābhārata 6.6.84.
Translation: Upanayan Sanskar should be given to a brahmin in the 8th year after their inception.
अग्नीन्धनं भैक्षचर्यामधःशय्यां गुरोर्हितम् ।
आ समावर्तनात् कुर्यात् कृतोपनयनो द्विजः ॥ १०८ ॥
Agnīndhanaṃ bhaikṣacaryāmadhaḥśayyāṃ gurorhitam |
ā samāvartanāt kuryāt kṛtopanayano dvijaḥ || 108 ||
The twice-born person, whose sacred thread Initiation has been performed, should continue to do, till the final Bath of “Return” (Samāvartana), lighting of fire (lighting a lamp everyday), showing respect for food (as if it is given to us as alms), sleeping on ground (not wishing for lavish beds) and always acting for the teacher’s well-being.
Manusmṛti 2.18,173.
What are the Responsibilities (Garud Puran)
Speaking about the appropriate way of performing ‘Upanayan sanskar’ (Sacred thread ceremony) rituals, Lord Vishnu said- " A Brahmin child should get consecrated with the sacred thread in his eighth year."
A dvija, whose ‘Upanayan sanskar’ has been performed, must face southwards while relieving himself in the night whereas during daytime he should face northward. Subsequently, he should purify himself by properly washing his hands and feet with soap and water. The purification is believed to be incomplete until and unless the rituals of ‘Aachman’ (ritualistic rinsing of the mouth) have been performed.
He should do ‘Pranayam’ and chant the sacred Gayatri mantra facing east in the morning.
In the evening he should chant Gayatri mantra facing south.
After this the ritual of ‘Bhikshatan’ is performed whereby he seeks alms and donates everything that he gets to his Guru as a mark of respect to him. This particular ritual is symbolic and emphasizes the necessity of subduing one’s ego before acquiring knowledge from his Guru.