Gematria is a method of exegesis (critical explanation or analysis of a text) used since the time of the Second Temple to derive insights into the sacred writings, to obtain interpretations of the text, or to illustrate a secular matter. The Hebrew language uses its letters to represent numbers. The first nine letters represent the numbers I to 9 respectively; the next 10 letters represent the numbers 10, 20... to 90; and the next four represent 100 to 400.
The cipher alphabet makes possible the method known in Hebrew as gematria. The term gematria is based on the Greek geometria. In talmudic times the rabbis began to mean by it "calculation" in general. In this sense, they used the numerical value of the letters of one word or verse to construct a different word or verse, the numerical value of whose letters equals that of the original passage, in order to give the original verse an added or a different meaning.
For example, in Genesis 32:5, Jacob sends a message to his brother, Esau, saying: "I sojourned with Laban". The Hebrew for "I sojourned" is "garti" , yod is 10, tav is 400, resh is 200, and gimmel is 3, adding up to a total of 613, which is the number of commandments specified in the Torah. In other words, the rabbis understood that Jacob was saying: "Although I sojourned with Laban, I kept the 613 commandments".
The Book of Revelation in the New Testament uses Gematria to disguise the name of the emperor Nero by writing the Greek form of his name in Hebrew characters, which gives it a total numerical value of 666, (Revelation 13:18).