How he wrote concerning the Erection of a Church, both to the Governors of the Provinces, and to the Bishop Macarius
Immediately after the transactions I have recorded, the emperor sent forth injunctions which breathed a truly pious spirit, at the same time granting ample supplies of money, and commanding that a house of prayer worthy of the worship of God should be erected near the Saviour's tomb on a scale of rich and royal greatness. This object he had indeed for some time kept in view, and had foreseen, as if by the aid of a superior intelligence, that which should afterwards come to pass. He laid his commands, therefore, on the governors of the Eastern provinces, that by an abundant and unsparing expenditure they should secure the completion of the work on a scale of noble and ample magnificence. He also dispatched the following letter to the bishop who at that time presided over the church at Jerusalem, in which he clearly asserted the saving doctrine of the faith, writing in these terms.
Source: Life of Constantine (New Advent)