Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
पूर्णिमादर्शयोर्नारीसेवनं परिवर्जयेत् ।दर्शे षष्ठ्यां प्रतिपदि द्वादश्यां प्रतिपर्वसु ॥ १४१ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 141.
Avoid being with a woman on the full moon and the new moon. Also on the new moon, the 6th, the 1st, the 12th and every parva (junction day) ...
Simple meaning: Avoid being with a woman on full-moon and new-moon days. The rule continues in the next verse.
नवम्यां च न कुर्वीत कदाचिद्दंतधावनम् ।
Never clean the teeth with a twig on these days. Oil massage rules begin for bad yoga and sign-entry days.
अर्कभौमदिने षष्ठ्यां नाभ्यंगो वैधृतौ तथा ।
No oil massage on Sunday, Tuesday, the 6th or bad yoga days. Rules for amla bathing follow.
पुत्रहानिर्भवेत्तस्य त्रयोदश्यां धनक्षयः ।
Amla bathing on the 10th risks grief over a son; the 13th, wealth; the 2nd, both.