The charism of Saint Faustina yielded not only the new school of spirituality but also the Apostolic Movement of the Divine Mercy. It undertakes in different manners her task of proclaiming to the world the message of Mercy through the testimony of life, deeds, words and prayer.
The idea of this Movement was revealed to Sister Faustina in Vilnius in 1935 when the Lord Jesus ordered her to set up a new congregation which will proclaim the mercy of God to the world and, by its prayers, obtain it for the world (Diary 436) Initially she claimed that she had to leave her congregation and set up a contemplative convent for which she wrote even a summary of convent rule. Gradually she recognized that the idea went far beyond one convent or congregation. In the beginning of 1936, she wrote in a letter to her spiritual director Rev. Michał Sopoćko, I can see clearly that there is going to be not only both a female and male congregation, but a great association of lay people which everybody can be a member of and thereby with his deeds remind others about God’s mercy and exercise mercy towards others. Please do not think that these thoughts are [mere] madness, for they are the sincere truth, which will shortly be carried out in deed, even if I would have no one in favour of this work; still, I am not discouraged by anything, for it is enough for me to know that this is the will of God. However she still claimed that her role in this work would be setting up a contemplative congregation. The desire of fulfilling of this task was the basis for passive nights (mind and will) in her life, after which she achieved full union with God: mystical betrothal and mystical marriage. Finally in her mystical experience she clearly recognized that the task, albeit one, would have three aspects. The first was that of cloistered religious orders, where souls separated from the world will burn as an offering before God’s throne and beg for mercy for the whole world …and by their entreaties, they will obtain blessings for priests, and through their prayers prepare the world for the final coming of Jesus (Diary 1155). The second aspect was that the religious congregations were to combine prayer with acts of mercy and in this egoistic world they will try to rouse up love, the mercy of Jesus (Diary 1156). The third aspect consisted in the fact that everyone in the world can belong to this group through prayer and deeds of mercy without any obligation to take vows. A member of this group, Sister Faustina wrote, ought to perform at least one act of mercy a day, but there can be many more, for such deeds can easily be carried out by anyone (Diary 1158).