The idea of "one divides into three" first appeared in which ancient book of China?

You may be talking about Lao Tzu's Tao Te Ching.

Chapter 42 of Lao Zi's Tao Te Ching: Tao gives birth to one, two, three and everything. Everything is negative and positive, and I rashly think it is peace. What people hate is loneliness, widowhood and ignorance, and the princes thought it was said. Therefore, things are either profitable or profitable. I also teach what others teach. I will regard him as the godfather.