I quoted from Bulgakov some posts ago; I now continue with a fitting extract for the day of Pentecost, a rich panoply of intense theological contemplation concerning Holy Mary, Mother of God, Vessel of the Holy Ghost, as image of the Church, as Mediatrix, Advocate and associate with Christ's Sacrifice:
Mary as the personal habitation of the Holy Spirit is in truth the true personal expression of the Church, the heart of the Church of which Christ is the Head. Overshadowed by the Holy Spirit, she becomes the Mother of God, brings forth the Logos, and in and through her this divine motherhood belongs to the whole Church: the Logos born of the Virgin is also born in the souls of the faithful, for every Christian soul has a part in the divine motherhood of the Mother-Church, Theotokos (cf. St Augustine). The Church and Mary each bear the same relation alike to Christ and Christians. It would be impossible to say in so many words that Mary is the Church, and yet it may be said that the Church is represented by Mary, in so far as in her person all the attributes of the Church find their personal, final, and most perfect embodiment.
The Mother of God has no need of prayer for herself, for as deified she is in possession of all things. As the glory of God and the glory of the world, as the manifested love of God for the world and the manifested love of the world for God, in her prayer she glorifies God [cf. her Magnificat]. Her own prayer is glorification, eternally realized love, flaming and triumphant in its perfect joy—God's own love for himself in his creation. But as the foremost representative of the world and of all creation, the Mother of God offers also a prayer which is not her own, and yet is hers as the prayer of all creation. She gives wings to its prayer; raising it to the throne of God, she gives it power; she is the intercessor raising her hands to God as a high-priestess (orante [a pray-er]) and overshadowing the world with her veil. The Mother of God is the praying Church itself in its personal embodiment, and in this sense she is the universal Mother, defender and guardian. She is personal, incarnate mercy and pity for the world in its creaturely shortcomings and sinful distortion. Being now absolutely free from these shortcomings and from the power of sin, she is the sunlit summit of the world, for she still belongs to it. The saints and the prayers of the saints surround this summit like a bright cloud and draw near to it. But even the angelic world and the greatest saints are separated from the Mother of God both by her perfect holiness and by her deification, that is, by the fact that in her creaturely shortcomings are completely overcome [though the angels and saints are likewise hallowed and deified, "star differeth from star in glory" - her holiness is greater by far than that of all others]: her own gracious life is the life of the Holy Spirit dwelling in her, and her vicarious life is the life of the whole created world to which she belongs. It is in this that her mediatory significance lies: she brings to her Son, the world's Saviour, the world which he has saved; its salvation is realized in and through her, and nothing in the world takes place apart from her. She has given flesh to her Son and she is herself the God-bearing flesh through which the flesh of the world is brought to him for salvation. In her submission to God's will she has spiritually sacrificed her Son's life to God, and as she stood by the cross she was silently continuing to say that which she had said once and forever: 'Behold the handmaid of the Lord.'
We must take the last step in following this line of thought and admit that the outpouring of the Holy Spirit upon all flesh takes place with the participation of the Mother of God, who for that reason was present at Pentecost. The central place she occupies in the Church precludes the possibility of anything in the life of the Church happening apart from her and not through her. Owing to her significance as the havitation of the Holy Spirit, the action of the Holy Spirit in the creature involves her co-operation.
— from S.N. Bulgakov, The Burning Bush (Kupina Nepolimaya) (1927), quoted, translated from the end of pp. 183-8 and from pp. 203-6 in the original Russian, in A Bulgakov Anthology, J. Pain & N. Zernov, edd. (London: SPCK, 1976), 95-6. [The notes in square brackets are my own.]