Its attitude in the controversy on the date of Easter (he wanted to preserve the Celtic habit against the system recommended by the pope), the hardness of the discipline which he professed and the reprimands which he addressed to the king Thierry II for his licentious life were worth him to be banished into 610: with its holy disciple Gall, it was installed on the edges of the lake of Constancy, to carry the Gospel in Alamans.

Saint Gall fixed itself definitively in Switzerland, while Colomban passed to Lombardy, where it founded the monastery of Bobbio (613), which became a high place of preaching for the Lombardic ones at the same time as an important center of intellectual life. The rule of Colomban saint, who stressed the ascetic practices, was supplanted soon by the rule of Benoît saint.