From the archives:
The Lord Jesus appeared to Blessed Maria Pierina de Micheli, a nun in the Institute of the Daughters of the Immaculate Conception, in 1938 and said to her,
Two years earlier, Jesus said to her, "I wish that my face, which reflects the deep pains of my soul, the sorrow and love of my heart, be better honored: who contemplates me consoles me."
Do you see how I suffer? Yet, very few understand me. Those who say they love me are very ungrateful! I have given my heart as the sensible object of my great love to men and I give My Face as the sensible object of my sorrow for all the sins of men. I wish that it be venerated by a special feast on Tuesday, the day before Ash Wednesday. I wish that the feast be preceded by a novena in which the faithful make reparation with me, joining together and sharing in my sorrow.
Blessed Maria Pierina de Micheli
Wishing to honor the Lord's request that his Holy Face be more widely honored and adored, on April 17, 1958 Blessed Pope Pius XII approved the Feast of the Holy Face of Jesus Christ to be observed on the Tuesday before Ash Wednesday and issued for its liturgical observance the texts of the Votive Mass in Honor of the Holy Face of Jesus Christ.
As I understand it, this votive Mass was initially allowed for particular religious institutes but was later extended for use throughout the Church, through the efforts of Fiorenzo Cardinal Angelini, by Blessed Pope John Paul II.