Srimad-Bhagavatam: Canto 12 - Chapter 1 - Verse 47
Sanskrit:
क्षीणायुष: क्षीणसत्त्वान् दुर्मेधान् वीक्ष्य कालत: ।वेदान्ब्रह्मर्षयो व्यस्यन् हृदिस्थाच्युतचोदिता: ॥ ४७ ॥
ITRANS:
kṣīṇāyuṣaḥ kṣīṇa-sattvāndurmedhān vīkṣya kālataḥvedān brahmarṣayo vyasyanhṛdi-sthācyuta-coditāḥ
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.