The first time that the heart of Mary is mentioned in the Gospel, it is to express all the richness of Our Lady's interior life. St Luke writes "Mary kept all these things, pondering them in her heart".

The preface of the Mass attributes a number of qualities to the heart of Mary. It is "wise", because she understood the meaning of the Scriptures as no other person had ever done, and she kept in her heart the memory of the words and things in relation to the mystery of salvation. It is "immaculate", that is, immune from any stain of sin. It is "docile" because she submitted so faithfully to God's will and to every one of His wishes. It is "humble" because she imitated the humility of Jesus, who said "Learn from me; for I am gentle and lowly in heart". It is "simple", free from any duplicity and full of the Spirit of truth. It is "clean" and so able to see God according to the words of the Beatitude. It is "firm" in the acceptance of the Will of God when Simeon announced to her that a sword of sorrow would pierce her heart or when she was at the foot of the Cross of her Son. It is "ready" for when her Son slept in the sephulchre; she kept watch in the expectation of the Resurrection. The Heart of Mary was above all the "Temple of the Holy Spirit" because of Her motherhood and because of her continuous acceptance of the Holy Spirit.