Bonaventure's De perfectione vitae ad sororesAs prayer is the spiritual teacher of the friars, and so that the spirit of devotion not grow cold in the friars but burn continuously and ever more intensely on the altar of their heart, and indeed just as the Seraphic Father desired that the true spiritual friar to pray always...
The substance of this passage from chapter three of the Capuchin Constitutions of 1536 recurs in all the versions of the Constitutions down to modern times prior to 1968. The Constitutions of 1968 (n.40) and 1975 (n.41) have instead:
In order to keep the spirit of prayer in us from becoming lukewarm and rather have it grow steadily in fervour, we need to apply ourselves daily to the practice of prayer.
Then in 2002, taking up the 1968 text, the Constitutions restore the reference prayer as the spiritual teacher:
52.3 Moreover, that the spirit of prayer may never grow cold within us but be ever more inflamed from day to day, we must give ourselves to its exercise in our daily lives...
52.6 Mental prayer is the spiritual teach of the brothers who, if they are true and spiritual lesser brothers, prayer ever more interiorly.
Perhaps it could be argued that the content of this particular passage has been somewhat impoverished since 1968.
A connection exists between the earlier version of this passage and Saint Bonaventure's accommodation of the text of Leviticus 6,12-16 in De perfectione vitae ad sorores, presented here, and De sex aliis seraphim.
As one source used in the formulation of the first Capuchin Constitutions, and as an authentic work of Bonaventure, one rarely translated to English, capdox offers a new English translation completed in November 2012. Go to capdox.