john 7:38 He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water. - Free Bible Online

      38. as the scripture hath said--These words belong to what follows, "Out of his belly, as the scripture hath said, shall flow," &c. referring not to any particular passage, but to such as Isa 58:11; Joe 3:18; Zec 14:8; Eze 47:1-12; in most of which the idea is that of waters issuing from beneath the temple, to which our Lord compares Himself and those who believe in Him.
      out of his belly--that is, his inner man, his soul, as in Pr 20:27.
      rivers of living water--(See on Joh 4:13). It refers primarily to the copiousness, but indirectly also to the diffusiveness, of this living water to the good of others.

JFB.