Basil of Caesarea — as excerpted in the Catena Aurea on Luke 13:22-30

“(in reg. ad int. 240.) For as in earthly life the departure from right is exceeding broad, so he who goes out of the path which leads to the kingdom of heaven, finds himself in a vast extent of error. (int. 241.). But the right way is narrow, the slightest turning aside being full of danger, whether to the right or to the left, as on a bridge, where he who slips on either side is thrown into the river.”