The privilege you are trying to grant is one that was first granted to you WITH GRANT OPTION. The user who made that grant is among the list of users in this present statement. For security reasons, you may not do a reciprocal grant. Rewrite the statement leaving out the name of your original patron. To see a list of the users to whom you may not grant, query systabauth as follows:
SELECT grantor FROM systabauth WHERE grantee = USER