From 1109 to 1134 he was standing before the third abbot of the Abbey of Citeaux. During this time the mother monastery of the Cistercians was a flourishing scriptorium in which Stephan Abt probably worked itself. The Cistercian thank Stephan Harding many texts, including the first version of its constitution, the Carta Caritatis, the Exordium parvum (the story of the founding of the monastery ) and a revision of the Bible. This work is also Bible of St.. Stephan Harding called and should create a single Bible text for all the monasteries of the Order. To 1113 Stephen Harding took the young Bernard of Clairvaux on in Citeaux. He was thus a spiritual father to Bernard. Stephan helped by his research on the Cistercian reform; he was involved in the creation of the Cistercian rite, on a purge of Hymnars through compositions, which he requested from Milan, as the Rule of St. Benedict explicitly mentions the Ambrosian hymns. Likewise, the breviary Stephen goes back to him.
When Stephan Harding died in 1134, was one of numerous Citeaux daughter monasteries, which were in turn become after the Cistercian Filiationsprinzip already mother monasteries. The Cistercian celebrate the Solemnity of the third abbot of Citeaux today along with its two predecessors Alberic and Robert of Molesme on 26 January. Until the reorganization of the Cistercian Kalendarium his feast day was celebrated on July 16.