Library Eusebius of Caesarea Life of Constantine
Book 3, Chapter 48: How he built Churches in Honor of Martyrs, and abolished Idolatry at Constantinople.
And being fully resolved to distinguish the city which bore his name with special honor, he embellished it with numerous sacred edifices, both memorials of martyrs on the largest scale, and other buildings of the most splendid kind, not only within the city itself, but in its vicinity: and thus at the same time he rendered honor to the memory of the martyrs, and consecrated his city to the martyrs' God. Being filled, too, with Divine wisdom, he determined to purge the city which was to be distinguished by his own name from idolatry of every kind, that henceforth no statues might be worshipped there in the temples of those falsely reputed to be gods, nor any altars defiled by the pollution of blood: that there might be no sacrifices consumed by fire, no demon festivals, nor any of the other ceremonies usually observed by the superstitious.
English translation by Ernest Cushing Richardson, in Nicene and Post-Nicene Fathers, Series II, Vol. I (eds. Philip Schaff and Henry Wace; Buffalo: Christian Literature Publishing Co., 1890). Public domain. Digital text via New Advent Church Fathers.