Augustine of Hippo

In order to attain that vision by which we see God as he is, he has warned us that our hearts must be cleansed. As objects are called visible in our fashion of speaking, so God is called invisible lest he be thought to be a material body. Yet he will not deprive pure hearts of the contemplation of his essence, since this great and sublime reward is promised, on the Lord's own word, to those who worship and love God. At the time when he appeared visibly to bodily eyes, he promised that his invisible being also would be seen by the clean of heart, "He that loves me shall be loved of my Father, and I will love him and will manifest myself to him." It is certain that this nature of his, which he shares with the Father, is equally as invisible as it is equally incorruptible.