Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 1 · Muhurta: Marriage, Home, Farming
ज्योतिःशास्त्रम्
श्राद्धी चाऽऽदित्यवारे तु सप्तजन्मस्वरोगभाक् ।संक्रान्तौ सूर्यवारो यः सोऽर्कस्य हृदयः शुभः
In the full Agni Purana this is chapter 195, verse 2.
One who does a shraddha (ancestor rite) on Sunday is free from illness for seven births. A Sunday that falls on a sankranti (the Sun's entry into a sign) is called the Sun's heart. It is good.
Simple meaning: A Sunday ancestor rite keeps illness away for seven births. A Sunday on a sankranti is good.
कृत्वा हस्ते सूर्यवारं नक्तेनाब्दं स सर्वभाक् ।
A Sunday vow in Hasta for a year gives everything. Seven Mondays in Chitra bring happiness.
स्वात्यां गृहीत्वा चाङ्गारं सप्तनक्त्यार्तिवर्जितः ।
Seven night meals on Mars's day in Svati free you of trouble. Seven on Mercury's day in Vishakha remove the planets' trouble.
अनुराधे देवगुरुं सप्तनक्ती ग्रहार्तिनुत् ।
Seven night meals on Jupiter's day in Anuradha and Venus's day in Jyeshtha remove the planets' trouble.