Direct biblical statement
Luke 2:16–19
Treasured in her heart
16 And they came with haste: and they found Mary and Joseph, and the infant lying in the manger.
17 And seeing, they understood of the word that had been spoken to them concerning this child.
18 And all that heard wondered: and at those things that were told them by the shepherds.
19 But Mary kept all these words, pondering them in her heart.
Douay–Rheims · Challoner revision · Luke 2:16–19
Why this matters
The shepherds witness the child and share what they have heard. Mary keeps and reflects on these events in her heart; her contemplative response is explicitly narrated.