Skandapurana 5.215.8

5.215.8

yasya svatejasā sūryaḥ proktastrailokyadīpakaḥ ..
tasminvasati yenenduramāvasyā tataḥ smṛtā .. 8 ..

Through its own splendor, the sun is called the illuminator of the three worlds; / because the moon dwells in that [ray], it is traditionally called the new moon (amāvasyā).