Ubi Arcano Dei Consilio §51

⁵¹ We scarcely dare to include, in so many words, in the program of Our Pontificate the reassembling of the Ecumenical Council which Pius IX, the Pontiff of Our youth, had called but had failed to see through except to the completion of a part, albeit most important, of its work. We as the leader of the chosen people must wait and pray for an unmistakable sign from the God of mercy and of love of His holy will in this regard. ( Judges vi, 17)