UPON MERIT.
Every good work can, as you know, have four qualities: it can be meritorious, satisfactory, consolatory, or impetratory.
In order to have the two first qualities it must be performed when we are in a state of grace; that is to say, through the motive of charity, or, at least, in charity.
But the two last it can have, although imperfectly, without charity; for how many sinners there are who feel consolation in doing works which are morally good, and how many who in praying impetrate graces and favours from the mercy of God.
Between the two first qualities of good works there is this difference, that the first abides with and belongs wholly and entirely to the person who performs the work, and cannot be communicated; that power of communication being reserved solely for the merits of Jesus Christ our Lord, which do not stop short, as it were, and end in Him, but can be, and, in fact, are, communicated to us. Neither the saints in heaven nor those on earth have power to communicate to us one tittle of their merits; not the former, because in glory they are rewarded far beyond their deserving; not the latter, because they have not yet reached the goal, and whatever sanctity they may possess, they may, through sin, fall away from it, and all have need of the grace and mercy of God to keep them from so falling.
The second quality, however, is communicable, because we can share in the necessities of one another, and can make satisfaction one for another; spiritual riches being no less communicable than temporal ones, and the abundance of some being able to relieve the starvation of others. Hear what our Blessed Father says on this subject in his eighteenth Conference: "We must never think that by going to Holy Communion for others, or by praying for them, we lose anything. We need not fear that by offering to God this communion or prayer in satisfaction for the sins of others we shall not make spiritual profit for ourselves. The merit of the communion and of the prayer will remain with us, for we cannot merit grace for one another; it is our Lord alone who can do that. We can beg for graces for others, but we can never merit them."