Joseph Gikatilla, Sha’arei Orah, Vol. 1, p. 167

Jewish Mysticism
Consider and know how deep the power of prayer is, and from which place it begins and to which it emanates forth as a chain. By means of prayer, properly performed, all of the sefirot are united, and the overflow pours forth from above to below, and the upper and lower entities are blessed by he who prays.

Translated by Hartley Lachter