Brihadaranyaka Upanishad 1.5.14

1.5.14

sa eṣa saṃvatsaraḥ prajāpatiḥ ṣoḍaśakalastasya rātraya eva pañcadaśa kalā dhruvaivāsya ṣoḍaśī kalā sa rātribhirevā ca pūryate'pa ca kṣīyate so'māvāsyām̐ rātrimetayā ṣoḍaśyā kalayā sarvamidaṃ prāṇabhṛdanupraviśya tataḥ prātarjāyate tasmādetām̐ rātriṃ prāṇabhṛtaḥ prāṇaṃ na vicchindyādapi kṛkalāsasyaitasyā eva devatāyā apacityai

This Prajâpati (Hiranyagarbha) has sixteen digits and is represented by the year. The nights (and days) are his fifteen digits, and the constant one is his sixteenth digit. He (as the moon) is filled as well as wasted by the nights (and days). Through this sixteenth digit he permeates all these living beings on the new moon night and rises the next morning. Therefore on this night one should not take the life of living beings, not even of a chameleon, in adoration of this deity alone.