WCF 26.2.
Saints by profession are bound to maintain an holy fellowship and communion in the worship of God, and in performing such other spiritual services as tend to their mutual edification; (Heb. 10:24–25, Acts 2:42, 46, Isa. 2:3, 1 Cor. 11:20) as also in relieving each other in outward things, according to their several abilities and necessities. Which communion, as God offereth opportunity, is to be extended unto all those who, in every place, call upon the name of the Lord Jesus. (Acts 2:44–45, 1 John 3:17, 2 Cor. 8–9, Acts 11:29–30)