Saint Patrick (c. 432 AD)
Saint Patrick was a fifth-century missionary to Ireland.
According to his own written testimony, he baptized thousands of converts.
His stated biblical basis for doing so was the now-disputed ending of Mark’s Gospel. Read below.
It is right that we should fish well and diligently, as the Lord directs and teaches when he says: “Follow me, and I will may you fishers of men.” And again he says through the prophets: “Behold, I send many fishers and hunters, says God”; and other such sayings.
Therefore it is very right that we should cast our nets, so that a great multitude and crowd will be taken for God. Also that there should be clerics to baptise and encourage a people in need and want.
This is what the Lord says in the gospel: he warns and teaches in these words: “Go therefore and teach all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you; and behold I am with you all days, even to the end of the age.” Again he says:
“Go out therefore to the whole world and announce the gospel to every creature. Whoever believes and is baptised will be saved; whoever does not believe will be condemned.”
Source: Saint Patrick’s Confessio, par. 40 [read online]