Rig 1.190.01

ऋतं च सत्यं चाभीद्धात्तपसोऽध्यजायत। ततो रात्र्यजायत ततः समुद्रो अर्णवः॥

Truth (of thought) and truthfulness (of speech) were born of arduous penance, thence was nightgenerated, thence also the watery ocean.