“he shall send his angels… And they shall gather together his elect” - Matthew 24:31

… We too, when we see the church torn apart by Satan’s craft, torn by the savagery of the wicked, upset by unholy doctrines, tossed by storms, we must learn to turn our eyes to this assembly. If the thing seems hard to believe, let the angelic force remind us: Though the church be now vexed by human malice, tossed between exiles and escapes of all kinds, smashed and broken even on the waves, wretchedly torn in pieces and losing all firm support on earth, we must persist in hope, for it is not by human means but by heavenly power… That the Lord will gather it in

(John Calvin, A commentary on the harmony of the gospels)

TLDR “I will build my church, and the gates of hell shall not prevail against it.”