The most famous appearance is
《诗经·桃夭》 ('Peach Tree Tender'), a wedding song from the Book of Songs (~1000 BCE).
桃之夭夭 ('the peach is lush') is also the source of the homophonous slang
逃之夭夭 (táozhīyāoyāo, 'to flee scot-free') - a pun where
桃 ('peach') was swapped for
逃 ('to flee').