Shiva Purana
पंचकृत्यमिदं वोढुं ममास्ति मुखपंचकम् । चतुर्दिक्षु चतुर्वक्त्रं तन्मध्ये पंचमं मुखम् ९ ।
In order to look after these five-fold activities (pañcakṛtya) I have five faces, four in the four quarters and the fifth in the middle.
english translation
paMcakRtyamidaM voDhuM mamAsti mukhapaMcakam । caturdikSu caturvaktraM tanmadhye paMcamaM mukham 9 ।
hk transliteration by Sanscript