He was then a devoted disciple of Jean du Vergier de Hauranne, abbot of Saint-Cyran and spiritual director of the monastery of Port-Royal.
When he was imprisoned in the Bastille on the orders of cardinal Richelieu (from 1638 to 1643), he declared Anthoine Singlin's spiritual training complete and made him his intermediary between prison and the nuns and Solitaires at the monastery.
When Jean du Vergier de Hauranne died in 1643, some months after leaving prison, Anthoine Singlin accepted the post of almoner and spiritual director of the community, despite his own wishes to live a more retired life.
Anthoine Singlin continued Saint-Cyran's work spiritually, gaining a great reputation due to his words' simplicity.
Edited by Anne-Claire Josse, Paris, Nolin, 2003, 553 p. Thérèse Monthéard, « Quelques personnages illustres » in Chroniques de Port-Royal n°54, 2004, p. 50-51.