FR. LUDOVICO BILLOT, S.J., De Ecclesiae Sacmmentis (Vol. I); Quaestio LXVI; Thesis XXIV - 1931:
Baptism of spirit (flaminis), which is also called of repentance or of desire, is nothing else than an act of charity or perfect contrition including a desire of the Sacrament, according to what has been said above, namely that the heart of everyone is moved by the Holy Ghost to believe, and to love God, and to be sorry for his sins.