Shiva Purana
त्रयोदश्यां सितायां तु कर्तव्यं निशि भोजनम् ॥ असितायां तु भूतायां तत्र कार्यं शिवव्रतैः ॥ १३॥
On the thirteenth day in the bright half, food shall be taken at night, In the dark half, it is forbidden to those who follow Śiva’s rites.
english translation
trayodazyAM sitAyAM tu kartavyaM nizi bhojanam ॥ asitAyAM tu bhUtAyAM tatra kAryaM zivavrataiH ॥ 13॥
hk transliteration by Sanscript