WCF 31.1.
For the better government, and further edification of the Church, there ought to be such assemblies as are commonly called Synods or Councils; (Acts 15:2,4,6) and it belongeth to the overseers and other rulers of the particular churches, by virtue of their office, and the power which Christ hath given them for edification and not for destruction, to appoint such assemblies; (Acts 15) and to convene together in them, as often as they shall judge it expedient for the good of the church. (Acts 15:22–23,25)