Sefer Yetzirah ספר יצירה
The oldest kabbalistic text: the world is created through «thirty-two paths of wisdom» — letters and numbers.
Sefer Yetzirah is a tiny book — some fifteen hundred words — and among the most enigmatic in the tradition. It states that the world was created through «thirty-two paths of wisdom»: ten sefirot and twenty-two letters, divided into three «mothers», seven doubles and twelve simples. The letters are mapped onto elements, planets, months and organs of the body, building a correspondence between speech, time and the human being.
Tradition ascribes it to Avraham and its editing to Rabbi Akiva; scholars date it anywhere from the mishnaic period to the early Middle Ages. Rav Saadya Gaon, the Raavad and Yehuda haLevi wrote commentaries on it.
The talmudic stories of sages who «created a calf» by studying the laws of creation belong to this book — and from them, centuries later, grew the legend of the Maharal's Golem.