SB 12.6.47
ksinayusah ksina-sattvan
durmedhan viksya kalatah
vedan brahmarsayo vyasyan
hrdi-sthacyuta-coditah
Translation:
Observing that people in general were diminished in their life span, strength and intelligence by the influence of time, great sages took inspiration from the Personality of Godhead sitting within their hearts and systematically divided the Vedas.