The Wiccan Rede (Short Version)
Eight words the Wiccan Rede fulfill, An' it harm none do what ye will.
Known now as the "short rede" or "short version", this is the original form of the Wiccan Rede that was published by Doreen Valiente in 1964, in line with Gerald Gardner's teachings. Since that time, several variations of the Rede have been published, but they all convey the same meaning. The Rede is not a literal commandment, but more along the lines of helpful advice. It places the responsibility of your actions with yourself (as opposed to some malevolent, supernatural force) and challenges you to truly explore the consequences or results of your decisions and deeds.
Where Gardner got the inspiration for the Rede is debated among scholars and historians. Some say it was inspired by Aleister Crowley's The Book of the Law, where the phrase, " Do what thou wilt shall be the whole of the Law", is found. Others contest it came from the fictional French title, The Adventures of King Pausole , where the main character, King Pausole, gives an edict that translates to, "Do not harm your neighbor; this being well understood, do that which pleases you." Still others liken it to the Latin maxim primum non nocere (first do no harm).
The Wiccan Rede (Long Version)
In 1974, a 26 line poem titled "The Wiccan Rede" was published in the now defunct pagan magazine, Earth Religion News, followed shortly by the publication of another poem by Lady Gwen Thompson titled "Rede of the Wiccae" in Green Egg Magazine. Lady Thompson claimed that her version was the original version and attributed it to her grandmother, Adriana Porter, however, this has been widely disproven. The 26 line poem became known as the "long version" or the "long rede". Several versions have since been passed around; some shorter, some longer. The long version expands to include common Wiccan beliefs, customs and practices. Check it out here.
The Rule of Three
Also known as the Threefold Law or the Law of Return, this is a tenet held by some Wiccans. It's basic premise is that whatever energy is sent out will return to the sender three times. This goes for good energy and bad energy alike, however, the nature of the threefold return varies among practitioners. Some believe that the return comes in three distinct instances, others that it is one return at three times the strength. Still others may have an entirely different interpretation of the return or not follow it at all, being more inclined to follow a more generic, karmic approach and feeling that the Law of Three is just an over-exaggeration or over-emphasis of the Wiccan Rede, which already makes us responsible for our actions. Regardless of the interpretation, the key takeaway here is that Wiccans believe in some kind of energetic return that is a reaction to our actions.
Wiccan Ethics
Like many prolific religions, Wicca has its own version of The Golden Rule called the Wiccan Rede and a set of ethical beliefs that set the tone for general practice.