Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · Signs, Planets, Birth
जातकम् १
त्रिकोणात्सांत्यधाधर्मायुः सुखखोद्यपः सुहृत् ।जीवो जीवज्ञौ सितज्ञौ व्यर्का व्याराः क्रमादमी ॥ २५ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 55, verse 25.
Count from a planet's mulatrikona (a planet's strong own-sign part) sign. The lords of the 12th, 9th, 8th and 4th from it are its friends, with some others. In turn from the Sun, the friends are these. Jupiter. Jupiter and Mercury. Venus and Mercury. All but the Sun. All but Mars. (Our text is unclear here: the other house words are damaged.)
Simple meaning: A planet's friends are counted from its own strong sign. The verse then names each planet's friends.
वींद्वर्का विकुजेंद्वर्काः सुहृदोऽन्ये रवेर्धृताः ।
Planets in the 2nd, 3rd, 4th, 10th, 11th or 12th from each other are friends for the moment.
स्वोच्चत्रिकोणगेहा प्रनवांशैस्थानजं बलम् ।
A planet is strong in its high sign, own sign and own navamsha. It also gets strength from a direction.
निशींदुकुजसौराश्च सर्वदा क्षोह्नि चापरे ।
Moon, Mars and Saturn are strong at night. The rest are strong by day. Bad planets gain in the dark half.