Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
मुहूर्तमानं द्वरावक्षणर्क्षाणि समेश्वरम् ।अर्यमा राक्षसब्राह्मौ पित्र्याग्नेयौ तथाभिजित् ॥ २२७ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 227.
That is the measure of a muhurta (48 minutes). The muhurtas go with stars and their lords. The bad ones are Aryama, Rakshasa and Brahma, Pitri (ancestors) and Agni, and Abhijit. (Our text is unclear here: the word 'dvarava' before 'muhurta stars'.)
Simple meaning: A muhurta is one fifteenth of day or night. The bad muhurtas for each weekday begin here.
राक्षसाख्यौ ब्राह्मपित्र्यौ भर्गाजांशाविनादिषु ।
Each weekday has one or two bad muhurtas. Skip them for good acts.
येषु ऋक्षेषु यत्कर्म कथितं निखिलं च तत् ।
An act told for a star can also be done in the hour of that star's god.
भूकंपः सूर्यभात्सप्तमर्क्षे विद्युच्च पंचमे ।
Counting from the Sun's star, some stars carry bad omen names: Earthquake, Lightning, Spear and Thunderbolt.