Here is a copy of an essay that Fr. Yves Congar wrote on the ancient theme of the Church as Mother: Congar Mother Church
The longer version, in French, of the article can be found at: Yves Congar, “Au lecteur,” in Karl Delahaye, Ecclesia mater chez les Pères des trois premiers siècles: Pour un renouvellement de la Pastorale d’aujourd’hui (Unam Sanctam 46; Paris: du Cerf, 1964) pp. 7-32. This preface to the French translation of the work is dated 3 September 1963. Reading it, one feels that after the drama of the first session of the Second Vatican Council, Congar was expressing a feeling of liberation, and of vindication.