The number 108 is a sacred number in Buddhism, but in other religions as well (Hinduism, Jainism). What exactly is the origin of 108 being a sacred number in Buddhism? Is there anything about it in the ancient scriptures? Did the Buddha say anything about it? Or is it more likely that this was incorporated from other older beliefs?
The number 108 comes from the Vedas - so it predates Buddhism by at least a millennium. I did a lot of research on the topic last year, and found that there were two major numerological memes in Asia: 7/21 and 27/108. The latter goes back to Vedas and the earlier seems to be of Chinese origins.
Interaction of two memes is reflected in design of Zen mala, which has 108 beads but positions marker beads at 7 and 21. Looks like Zen mala was designed by people who already had 7 as their sacred number by the time Buddhism came to them. For them reciting prayers 7 times, doing prostrations 7x3 times etc. felt very natural, so they thought that adding numbers 7 and 21 to the foreign 108-bead Buddhist mala was a great convenience feature. For these people, number 108 remained somewhat alien and less important than their traditional number 7. (The Japanese still celebrate 7th day after baby's birth, mourn the 7th day after death, recognize 7 spring herbs and 7 lucky gods. The Chinese increment person's age on 7th day of the year, eat 7 good luck dishes, their version of Valentine's day is on 7th day of 7th lunar month etc.)
The two traditions must have existed independently in different parts of Asia, until Buddhism started spreading outside of India, carrying Hindu memes on its back (mantras, rituals etc) -- so in countries other than India number 108 became identified with Buddhism exclusively, while in India it remains a generic lucky number until this day.
The origin of 108 in the ancient buddhist scriptures seems to be from the total number of feelings classified in different ways by the Buddha:
"Monks, I will teach you a one-hundred-and-eight exposition that is a Dhamma exposition. Listen & pay close attention. I will speak."
"As you say, lord," the monks responded.
The Blessed One said: "And which one-hundred-and-eight exposition is a Dhamma exposition? There is the exposition whereby I have spoken of two feelings, the exposition whereby I have spoken of three feelings... five... six... eighteen... thirty-six... one hundred and eight feelings.
"And which are the two feelings? Physical & mental. These are the two feelings.
"And which are the three feelings? A feeling of pleasure, a feeling of pain, a feeling of neither pleasure nor pain. These are the three feelings.
"And which are the five feelings? The pleasure-faculty, the pain-faculty, the happiness-faculty, the distress-faculty, the equanimity-faculty. These are the five feelings.
"And which are the six feelings? A feeling born of eye-contact, a feeling born of ear-contact... nose-contact... tongue-contact... body-contact... intellect-contact. These are the six feelings.
"And which are the eighteen feelings? Six happiness-explorations, six distress-explorations, six equanimity-explorations. These are the eighteen feelings.
"And which are the thirty-six feelings? Six kinds of household happiness & six kinds of renunciation happiness; six kinds of household distress & six kinds of renunciation distress; six kinds of household equanimity & six kinds of renunciation equanimity. These are the thirty-six feelings.
"And which are the one hundred and eight feelings? Thirty-six past feelings, thirty-six future feelings, and thirty-six present feelings. These are the one hundred and eight feelings.
"And this, monks, is the one-hundred-and-eight exposition that is a Dhamma exposition."
There is also a reference to 108 Craving-verbalizations in AN 4.199, Discourse on Craving (Taṇhā-suttaṃ).
I have heard from an Indian friend who is an ordained Buddhist why there are 108 beads on a Mala. 108 signifies:
- There are six incoming senses and sensations: eyes, ears, touch, taste, smell and what the mind takes hold of.
- There are three types of sensation: pleasant, unpleasant and neutral. (6 times 3 = 18)
- There are three time zones in which we receive these incoming sensations: past, present and future. (18 times 3 = 54)
- There are two ways of dealing with these incoming sensations. (2 times 54 = 108)