The Teaching of the Twelve Apostles, or (from the Greek) the Didache, is an early Christian document of the first century, perhaps before the year 80, quite possibly earlier than some of the Gospels. It falls into three parts: the first is the “Two Ways”, the Way of Life and the Way of Death; the second part covers baptism, fasting, and Holy Communion; and the third speaks of the ministry. Eusebius judged it not to be part of the canon of Scripture (he was also doubtful of the Apocalypse), while Athanasius and Rufinus place it among the deutero-canonical works. Many of the Church Fathers were aware of it, and referred to it explicitly or implicitly. The text was lost for many centuries: it was rediscovered by a Greek bishop in 1873.

The theological virtue of hope is symbolized by the colour green, just as the burning fire of love is symbolized by red. Green is the colour of growing things, and hope, like them, is always new and always fresh. Liturgically, green is the colour of Ordinary Time, the orderly sequence of weeks through the year, a season in which we are being neither single-mindedly penitent (in purple) nor overwhelmingly joyful (in white).