Rigyajuh samatharbakhyah veda chatwara uddhritah
Itihasa puranancha panchamo Veda uchyate
Rig, Yaju, Sama, Atharva-the four names of the Vedas, Uddhrita-made into separate parts, Itihasa-historical records (Mahabharat), Puranancha-and the puranas, Panchama-the fifth, Veda-the original source of knowledge, Uchyate-is said.
The four divisions of the original sources of knowledge the Vedas were separately made. But the historical facts and authentic stories mentioned in the Puranas are called the fifth Veda.