How can one doubt that especially now, on Golgotha, this expression goes to the very heart of the mystery of Mary, and indicates the unique place which she occupies in the whole economy of salvation? (faith.org.uk)
It aims directly at the heart of the mystery that is a child. (firstthings.com)
When Guildenstern protests that he can not play the pipe, Hamlet rages: «You would play upon me; you would seem to know my stops; you would pluck out the heart of my mystery; you would sound me from my lowest note to the top of my compass; and there is much music, excellent voice, in this little organ; yet you can not make it speak. (firstthings.com)