Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 8 · Marriage
विवाहः
त्रिंशांशो बलवांस्तस्माद्वीक्ष्यमेतद्बलाबलम् ।शुभेक्षितयुताः शस्ता उद्वाहेऽखिलराशयः ॥ ४३२ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 432.
The trimshamsha (one-thirtieth of a sign) is stronger than that. So look at this strength and weakness. For marriage, all signs are good when joined or looked at by good planets.
Simple meaning: The thirtieth part is strongest. All signs are good for marriage if good planets join or see them.
चंद्रार्केज्यादयः पच यस्य राशेस्तु खेचराः ।
A lagna is good when the Moon, Sun, Jupiter and the others help it.
जामित्रशुद्ध्यैकविंशन्महादोषविवर्जितम् ।
Pick a lagna free of 21 great faults and with a pure 7th house.
वक्ष्यंतेऽत्र समासेन शृणु नारद सांप्रतम् ।
Now the 21 faults are told. The first is an impure almanac.