Catechism of the Catholic Church §281 — excerpt
And so the readings of the Easter Vigil, the celebration of the new creation in Christ, begin with the creation account; likewise in the Byzantine liturgy, the account of creation always constitutes the first reading at the vigils of the great feasts of the Lord.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: Egeria, Peregrinatio at loca sancta 46: PLS 1, 1047 · St. Augustine, De catechizantis rudibus 3, 5: PL 40, 256