Matthew 24:12

Matthew 24:12. Because iniquity (or ‘lawlessness') shall be multiplied. A horrible state of immorality prevailed in the first century, and the false teachers endeavored to join it with Christian profession ; the inevitable result was a coldness, a dying out of Christian love.

The love of the many (the mass) shall wax cold. So far as we know, this was not literally fulfilled in the first century. We infer that the entire fulfilment will come in with the great Apostasy (2 Thessalonians 2:3-8). The principle is: wickedness destroys love; immorality eats out the heart of Christianity.