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Where the Church has thus given her approval to any particular private revelation, it is no longer permitted to ridicule or to despise it. “Fas non est,” says Card. Franzelin, “tales revelationes contemnere” (de div. trad. 22). To do so were to fail in the respect due to the Church….

Pope Benedict XIV…: "When the Church has examined and approved these visions, no one may any longer doubt their supernatural and divine origin."

CANON 1395

Sister Faustina Kowalska: Writings (Holy Office, 6 March, 1959) AAS 51-271.

A Notification by tbe Holy Office:

The Supreme Sacred Congregation of the Holy Office, having examined the alleged visions and revelations of Sister Faustina Kowalska of the Institute of Our Lady of Mercy, who died in 1938 near Cracow, has decreed as follows:

1. The distribution of pictures and writings which present the
devotion to the Divine Mercy in the forms proposed by this
Sister Faustina, should be forbidden;

2. It is left to the prudent discretion of the Bishops to remove
such pictures which may have been already exposed for worship.
From the Holy Office, 6 March, 1959.

AAS 51-271; Holy Office, Notification, 6 March, 1959.

On June 30, 1978, The Sacred Congregation for the Doctrine of the Faith (A.A.S. page 350) published a "Notification" signed April 15, 1978, by His Eminence Franjo Cardinal Seper, Prefect, and Archbishop Jerome Hamer, O.P., Secretary. It is as follows:

From various places, especially from Poland, even proceeding from competent authority, it has been asked whether the prohibitions contained in the "Notification" of the Sacred Congregation of the Holy Office, published in the Acts of the Apostolic See, in the year 1959, p. 271, regarding the devotion to The Divine Mercy in the forms proposed by Sister Faustina Kowalska, must be regarded as still in force.

This Sacred Congregation, having now in possession the many original docuмents, unknown in 1959; having taken into consideration the profoundly changed circuмstances, and having taken into account the opinion of many Polish Ordinaries, declares no longer binding the prohibitions contained in the quoted "Notification." On July 12, 1979, in response to the Superior General of the Congregation of Marians of the Immaculate Conception of the B.V.M., who in the name of the Provincial Superior of the American Province of St. Stanislaus Kostka, of said Congregation, had asked for an authoritative explanation of the scope of the text in the "Notification" of 1978, rescinding the prohibitions to spread the devotion to The Divine Mercy proposed by Sister Faustina Kowalska, the Prefect of The Sacred Congregation for the Doctrine of the Faith ascertained:

... I have the honor of informing you that with the new "Notification" (A.A.S., 30 June 1978, p. 350)... it was the intention of the Holy See to revoke the prohibition contained in the preceding "Notification" of 1959 (A.A.S., 1959, p. 271), in virtue of which it is understood that there no longer exists, on the part of this S. Congregation, any impediment to the spreading of the devotion to The Divine Mercy in the authentic forms proposed by the Religious Sister mentioned above [The Servant of God Sister Faustina Kowalska].”