Question Seven
Whether those detained in Purgatory can in any manner sin mortally or venially
It is doubted whether souls in Purgatory can sin mortally, or at least venially, through impatience or through some other act.
To this it is answered as follows. Since it has been shown that as a soul departs from the body, so it is presented in the particular judgment, if souls are separated from their bodies in charity they are so confirmed in that charity that they can no longer sin or fall away from it, because “where the tree has fallen, there it shall be,” Ecclesiastes 11.
This is the common opinion and the ordinance of God, who has disposed that every human being who dies finally outside charity is to be damned and that one who dies finally in charity is simply to be saved. Such souls cannot afterward be bent toward impatience in their punishments, sin mortally, contract a venial fault from any source, and thereby prolong their punishments.
For they do not possess the tinder from which venial sin is caused, as Thomas says in Book IV, distinction 21, question 1, article 1.
The steadfastness, immunity from precipitous fall, and impeccability of souls existing in Purgatory can also arise from the fact that, made certain of their beatitude, they tolerate the punishments which they know to have been inflicted upon and owed by them through the just and merciful judgment of God, with the greatest patience and thanksgiving.
These things are from Lord Henry of Hesse upon Genesis.
Addition
Examine the book On the State of the Soul Departing in Charity, upon the Offertory of the Mass for the Dead, printed at Bologna, where I have also recorded both this matter and many other things concerning souls existing in Purgatory.