From the 1839 Constitutions of the Society of Mary: 19. 

By the vow of stability the member intends constituting himself permanently and irrevocably in the state of servant of Mary. This vow is in reality a devotedness to the Blessed Virgin with the filial design of spreading her knowledge and perpetuating her love and her cult as much as possible, by one’s self and by others, in whatever circumstances of life he may be. 20. Moreover, the vow of stability is made with the intention of never depriving the Society one’s cooperation in the work that has been undertaken. Dispensation from this vow can give rise to grave injustice to the Society. The Apostolic Letters require that those concerned in a vow take the steps necessary for a dispensation from it. 21. Whether it be expressed or not, the vow of stability is supposed in all orders. The Society of Mary deliberately makes it a special vow, which has the same consequences it includes everywhere else.