What follows is my provisional translation (in other words, not official or authorized; see here for more) of a prayer of ʻAbduʼl-Bahá, the original text of which is published in Muntakhabátí az Makátíb-i-Ḥaḍrat-i-ʻAbdu’l-Bahá, vol. 2, p. 3 (selection no. 5).
O God! Make this union to be the cause of heavenly blessings, and the means of enkindlement with the fire of Thy love in the eternal Kingdom. Grant a measure of grace that will draw them both nigh unto Thy sacred threshold and keep them firm in Thy love. Thereby may they progress day by day in spiritual degrees, and become two clear tokens of faith and certitude amidst all creatures. Praise be to God, the Lord of the worlds.
A typescript of the original Persian text of this prayer appears below (punctuation mine).