June 4. "Today is the Feast of the Most Sacred Heart of Jesus. During Holy Mass, I was given the knowledge of the Heart of Jesus and of the nature of the fire of love with which He burns for us and of how He is an Ocean of Mercy. Then I heard a voice: Apostle of My mercy, proclaim to the whole world My unfathomable mercy. Do not be discouraged by the difficulties you encounter in proclaiming My mercy. These difficulties that affect you so painfully are needed for your sanctification and as evidence that this work is Mine. My daughter, be diligent in writing down every sentence I tell you concerning My mercy, because this is meant for a great number of souls who will profit from it. "
(Saint Faustina's Diary, 1142)