This may help
St. Ambrose, De mysteriis, 390-391 A.D.:
“You have read, therefore, that the three witnesses in Baptism are one: water, blood, and the spirit; and if you withdraw any one of these, the Sacrament of Baptism is not valid. For what is water without the cross of Christ?
A common element without any sacramental effect. Nor on the other hand is there any mystery of regeneration without water: for ‘unless a man be born again of water and the Spirit, he cannot enter the kingdom of God.’ [John 3:5]
Even a catechumen believes in the cross of the Lord Jesus, by which also he is signed; but, unless he be baptized in the name of the Father and of the Son and of the Holy Spirit, he cannot receive the remission of sins nor be recipient of the gift of spiritual grace.”