Comes from 《
尚书·
盘庚上》 (the Book of Documents):
若火之燎于原,
不可向迩 ('like fire blazing across the plain, none can approach it'). The full chengyu
星星之火,
可以燎原 (xīngxīng zhī huǒ, kěyǐ liáoyuán, 'a single spark can start a prairie fire') was made famous by Mao Zedong in his 1930 essay of the same name.