Bede — on Gen 6:17 (Commentary on Genesis (Hexaemeron))

“Behold, I will bring the waters of a flood upon the earth, to destroy all flesh in which there is the breath of life under heaven. Everything that is on the earth shall perish, and I will establish my covenant with you, and you shall enter the ark, you and your sons, and the rest. The waters of the flood brought upon the earth killed all flesh that was found outside the ark, but Noah and all that were in the ark were saved. Washing the world with the water of baptism saves whomever it finds faithfully abiding in the unity of the holy Church; but those who receive baptism outside the Church from heretics or schismatics die unless they repent by returning to catholic unity. Likewise, when the time of the final judgment comes, whoever is found persevering in faith and action in the holy Church shall be saved eternally; those separated from the Church by faith, action, or both, perish.”