This is taken from one of my commentaries.
This is referring to Luke 1.
Mary, Ark of the Covenant
Luke’s Gospel tells us more about the Mother of Jesus, than any other book in the NT. Most of this information is packed within his first two chapters, where Luke strings together some of the most beautiful traditions we have about her life and mission. The deeper we delve into LUke’s narrative, the more we appreciate the way in which Luke tells us the story of Mary. One example of this is found in the story of the Visitation. On one level, it ells of a joyous encounter between two expectant mothers; on another, it recalls memorable stories told in the OT about the Ark of the Covenant. By alluding to these ancient traditions, Luke expands the vision of the careful reader considerably. For he leads us to see Mary as the Ark of God’s New Convenant and implies that the sacred Ark of the Old Covenant merely prefigured a more wonderful Ark to come: The Mother of the divine Messiah.
One tradition that Luke draws upon is from 2 Samuel. He intentionally sets up the sublt but significant parallels between Mary’s Visitation with Elizabetn and David’s effort to bring the Ark of the Covenant to Jeruslaem narrated in 2 Sam 6. When Luke tells us that Mary “arose and went” into the Judean hill country to visit her inswomn [Luke 4:39], he reminds us of how David “arose and went” into the Judean hill country centuries earlier to retrieve the Ark [2 Sam 6:2] Upon Mary’s arrival, Elizabeth is struck by the same sense of awe and unworthiness before Mary [Luke 1:43] that David felt standing before the Ark of the Covenant - 2 Sam 6:9]. Parallels continue as the joy surrounding this great encounter causes the infant John to leap with excitement [Luke 1:41], much as David danced with excitement before the Ark 2 Sam 6:16]. Finally, Luke addsd that Mary stayed in the “house of Zechariah” for “three monthes” [Luke 1:40, 56], recalling how the Ark of Covenant was temporarily stationed in the “house of Obed-edom” for a waiting period of “three monthes” [2 Sam 6:11] Taken together, these parallels show us that Mary now assumes a role in salvation history that was once played by the Ark of the Covenant. LIke this golden chest, she is a sacred vessel where the Lord’s presence dwells intimately with his people.
Luke also draws upon a second tradition from the Books of Chronicles. This time he brings into his stoay a highly significant expression once connected with the Ark. The term shows up in Luke 1:42, where Elizabeth bursts out with an exuberant cry at the arrival of Mary and her CHild. Although the Greek very translated as “exlaimed” seems ordinary enough, it is hardly ever used in the Bible. IN fact, it is found only here in the entire NT. Its presence in the Greek OT is likewise sparse, appearing only five times. Why is this important? Because every time the expression is used in the OT, it forms part of the stories surrounding the Ark of the Covenant. In particular, it refers to the melodic sounds made by Levitical singers and musicians why they glorify the Lord in song. It thus describes the “exulting” voice of instruments that were played before the Ark as David carried it in procession to Jerusalem 1 Chron 15:28; 16:4-5] and as Solomon transferred the Ark to its final resting place in the Temple 2 Chron 5:13] Alluding to these episdoes, LUke connects this ame expression with the melodic cry of another Levitical descendant, the aged Elizabeth [Luke 1:5] She too lifts up her voice in liturgical praise, not before the golden chest, but before Mary. Luke’s remarkable familiarity with these ancient stories enables him to select even a single word that will whisper to his readers that this young Mother of the Messiah is the new Ark of the Covenant.
For the reader with eyes to see and ears to hear, Luke has given us a vision of the Birign Mary that becomes ever more glorious the deeper we dig into the Scriptures. Our ability to see Mary as he did depends in part on our knowledge of the OT and in part on our snesitivity to Luke’s skillful use of it. By choosing his words and phrases carefully, he is able to weave various strands of biblical tradition into his narrative, adding beauty and depth to this already elegant prose. Little wonder the Church’s liturgical and theological traditions have so often described Mary as the Ark of the New Convenant. This vision is not merely the fuirt of mystical speculation from a later age. It is already embedded within the Infancy Narrative of Luke’s Gospel.
I wanted to go and look up the answer before I answered your question. Yes it is referring to Mary as the Ark of the Covenant. The meaning is hidden but it is there nevertheless as the preceeding paragraphs point out.
God bless.
[ps. I am sorry if there are any mispelled words, its hard to type from a copy without looking at the scree sometimes.]