<Gratian I and II C.16 q.1 c.45 [taken from different source], Sg omits this canon in C.17 (C.16)>.

§ <fol. 111> Quibus uero debentur plebibus? Illis, a quibus baptisma accipiunt, an aliis? Nos eos baptizamus, et uos ab eis decimas accipitis?

From which flock, indeed, are tithes owed?  From those who received baptism or from others?  We baptize them and you receive tithes from them?