The four divisions of the original sources of knowledge [the Vedas] were made separately. But the historical facts and authentic stories mentioned in the Purāṇas are called the fifth Veda. ।। 1-4-20 ।।
english translation
मूल ज्ञान के स्रोतों (वेदों) के चार पृथक् विभाग किये गये। लेकिन पुराणों में वर्णित ऐतिहासिक तथ्य तथा प्रामाणिक कथाएँ पंचम वेद कहलाती हैं। ।। १-४-२० ।।
hindi translation
RgyajuHsAmAtharvAkhyA vedAzcatvAra uddhRtAH | itihAsapurANaM ca paJcamo veda ucyate || 1-4-20 ||