Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 7 · Samskara Muhurtas
संस्कारमुहूर्ताः
उद्वाहेऽखिलवारर्क्षतिथिषु क्षौरमिष्टदम् ।कर्तव्यं मङ्गलेष्वादौ मङ्गलाय क्षुरार्पणम् ॥ ३४३ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 343.
At a wedding, shaving is good on all weekdays, stars and tithis (moon days). At the start of any lucky rite, offer the razor first, for good luck.
Simple meaning: At a wedding shaving is allowed on any day. In lucky rites the razor is offered first.
नवमे सप्तमे वापि पञ्चमे दिवसेऽपि वा ।
Choose the 9th, 7th, 5th or 3rd day before the rite, a good star, weekday and lagna.
आधानादष्टमे वर्षे जन्मतो वाग्रजन्मनाम् ।
The sacred thread is tied in the 8th year for Brahmins, the 11th for kings and the 12th for Vaishyas.
जन्मतः पंचमे वर्षे वेदशास्त्रविशारदः ।
The sacred thread in the 5th year can make a boy learned and prosperous.