The Didache is one of the oldest, if not the single oldest piece of Christian writing that has been found to date. It is commonly dated to around the year 100, and it is thought to be an early catechism. Some of the Fathers of the Church considered it part of the New Testament canon, and while it was ultimately not included in the canon of Scripture (except for the Ethiopian Orthodox, who seem to have a much broader Canon than the rest of orthodox Christianity), it does provide an invaluable look into the early Church, and especially giving us a glimpse into how the more Jewish form of Christianity developed into its own distinct Faith.
The first part of the Didache is considered by many scholars to be part of an older Jewish manuscript which was adapted later for Christian purposes.
Especially notable in my opinion is the specific condemnation of abortion contained in the second chapter.
"And this is the second commandment of the teaching: you shall not kill; you shall not commit adultery; you shall not corrupt children, nor practice sexual deviation; you shall not steal; nor practice calling on spiritual guides; nor use sorcery; you shall not procure an abortion, nor practice infanticide; you shall not covet your neighbor's goods.
You shall not commit perjury, nor accuse someone falsely; you shall not speak evil nor hold a grudge. You shall not be double minded nor double tongued, for the double tongue is the snare of death. Your word shall not be false or empty, but do what you say.
You shall not be covetous or extortionate, or hypocritical, or malicious or proud. You shall not plan evil against your neighbor. You should not hate anyone; but you should reprove some, and you should pray for some, and you should love some more then your own life."
Of course we know as Catholics, that a specific condemnation of abortion is unnecessary, since it falls directly under the prohibition of murder. I suppose that is further evidence that the Didache was intended as a catechism; converts may not necessarily have been aware that abortion is indeed murder.
Also significant is the condemnation of sorcery, divination, and use of mediums. This, we recall, is in the Bible in a few different sections (for example Exodus 22, 1 Samuel 28, Revelation 22), but we can take this as evidence that, while as Christians we're not necessarily called upon to put witches to death any longer under the old Law, we are certainly not to tolerate their evil practices.
I think my favourite part though, is this bit: "You should not hate anyone; but you should reprove some, and you should pray for some, and you should love some more then your own life."
As Catholics who are active on the internet, we probably hear several times a day somebody harping on us for being uncharitable... and sometimes they're right, sometimes we are, but sometimes we're saying things that need to be said. To allow error and blasphemy and heterodoxy to go uncorrected is far greater an injustice than correcting it, even if the correction seems harsh at the time. At the end of the day, a correction made in the spirit of Christian charity is directed towards helping the other party to come to the Faith, or to deepen their Faith and their love of God.
I think it's especially important to inspire our Catholic brethren to greater reverence in the context of the Holy Mass. If I could convince everyone I encounter of one thing, that would be it. I am reminded of what Cardinal Arinze said with regards to receiving the Eucharist kneeling. "If we believe, if we truly believe that it is Jesus, the Son of God, then why don't we kneel, why don't we crawl?"
Here is the video of him saying that:
(Skip to about 2:10 if you don't want to watch the whole thing.)
Basically what Cardinal Arinze says in this video, and which I agree with 120% is that if we truly love and respect and fear our God, that we should show it with our actions. It's simple, but so often forgotten, or even denied. Those who say it are labelled as Pharisees, or spiritually prideful. No, we're not. We believe that our exterior actions reflect and influence our interior disposition. That is why we kneel before Christ in our Holy Eucharist. That's why we genuflect towards Him in the Tabernacle, and receive Him kneeling, or at the very least bow, if you must stand.
As we read in Redemptionis Sacramentum: "The Mystery of the Eucharist is too great for anyone to permit himself to treat it according to his own whim, so that its sacredness and its universal ordering would be obscured." We are responsible for doing our part that the great Sacrament is never trivialized. We should fall down and worship Him, not treat the Mass like a community gathering or prayer meeting or an empty ritual.
So I will keep the Didache in mind. I will never hate, though I will sometimes reprove, in the spirit of charity and faithful correction. I will do so with prayer, and with a love greater than my own life.