“Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the holy Spirit”

-Matt 28:19

"Holy Baptism is the basis of the whole Christian life, the gateway to life in the Spirit (vitae spiritualis ianua), and the door which gives access to the other sacraments. Through Baptism we are freed from sin and reborn as sons of God; we become members of Christ, are incorporated into the Church and made sharers in her mission: "Baptism is the sacrament of regeneration through water in the word."

-CCC 1213

"By virtue of the Holy Spirit, baptism immerses us in the death and resurrection of the Lord, drowning the old man — dominated by the sin that divides us from God — in the baptismal font and giving birth to the new man, recreated in Jesus. In Him, all the sons of Adam are called to new life."

-Pope Francis
Pope Francis "General Audience." 11 April 2018, https://www.vatican.va/content/francesco/en/audiences/2018/documents/papa-francesco_20180411_udienza-generale.html

"Baptism is the door of the spiritual life and the gateway to the sacraments."

-St. Thomas Aquinas
III, q.73, 3 - Summa Theologica (1265–1274)