Saint Margaret Mary Alacoque was a Visitation nun who, in the year 1675, received from Our Lord, Who appeared to her out of the depths of the Blessed Sacrament, the assignment to be the great apostle of the public veneration of His Most Sacred Heart. Her spiritual supporter and director was a saintly priest of the Society of Jesus, Blessed Claude de la Colombiere. He died eight years before her. Our Lord told Saint Margaret Mary that He received in the Blessed Eucharist only irreverence and ingratitude. It was to her that Our Lord made the request that the Friday after the octave of Corpus Christi be set aside as a special feast in honor of the Sacred Heart. It was to Saint Margaret Mary that Jesus made the request that Catholics receive Him in Holy Communion on each first Friday of the month, and keep the Holy Hour on the night before the first Friday with the Blessed Sacrament exposed.
The great apostles of the feast of Corpus Christi and the feast of the Sacred Heart were girls; both were nuns. It was Blessed Juliana of Cornillon, an Augustinian nun who died in 1258 in Belgium, who was chosen by God to work for the institution of the feast of Corpus Christi. It was Saint Margaret Mary, a Visitation nun who died in 1690, who was chosen by God to work for the institution of the feast of the Most Sacred Heart.