Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 7 · Samskara Muhurtas
संस्कारमुहूर्ताः
स्वकुलाचारधर्मज्ञो माघमासे तु फाल्गुने ।विधिज्ञश्चार्थवांश्चैत्रे वेदवेदांगपारगः ॥ ३५३ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 353.
In Magha, he knows his family customs and duty. In Phalguna, he knows the rules. In Chaitra, he becomes wealthy and masters the Veda and its limbs.
Simple meaning: A thread rite in Magha brings family knowledge, in Phalguna knowledge of rules, in Chaitra wealth and learning.
वैशाषे धनवान्वेदशास्त्रविद्याविशारदः ।
A thread rite in Vaishakha brings wealth and learning. In Jyeshtha it brings strength and skill in rites.
शुक्लपक्षे द्वितीया च तृतीया पंचमी तथा ।
For the thread ceremony, choose the 2nd, 3rd, 5th, 7th, 10th or 13th day of the bright half.
श्रेष्ठा त्वेकादशी षष्ठी द्वादश्यन्यास्तु मध्यमाः ।
The 11th, 6th and 12th days are best. In the dark half, only the 2nd, 3rd and 5th are fine.