The three voids or immaterialities. The first set of three is (a) 空, (b) 無相, (c) 無願, v. 三三昧. The second, (a) 我空 , (b) 法空 , (c) 俱空 the self, things, all phenomena as "empty" or immaterial. The third relates to charity: (a) giver, (b) receiver, (c) gift, all are "empty".