Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 8 · Marriage
विवाहः
कुनवांशो महापातो वैधृतिश्चैकविंशतिः ।तिथिवारर्क्षयोगानां करणस्य च मेलनम् ॥ ४३९ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 439.
A bad navamsha (one-ninth part of a sign), Mahapata and Vaidhriti: these make 21. Now the coming together of five parts: tithi (moon day), weekday, nakshatra (star), yoga (Sun-Moon yoga of the almanac) and karana (half of a moon day)
Simple meaning: The last faults are a bad navamsha, Mahapata and Vaidhriti. The five almanac parts come next.
पंचांगमस्य शुद्धिस्तु पंचांगशुद्धिरीरिता ।
A lagna with a fault in any almanac part is worth nothing.
त्यजेत्पंचैष्टिकं चापि विषसंयुक्तदुग्धवत् ।
Drop the five-fold fault. The lagna and its navamsha should be seen or joined by their own lords.
न चेद्वान्योन्यपतिना शुभमित्रेण वा तथा ।
If no lord or friendly planet sees the lagna and navamsha, the groom's life may be at risk.