In canon law, commendam (or in commendam) was a form of transferring an ecclesiastical benefice in trust to the custody of a patron. The phrase in commendam was originally applied to the provisional occupation of an ecclesiastical benefice, which was temporarily without an actual occupant, in contrast to the conferral of a title, in titulum, which was applied to the regular and unconditional occupation of a benefice.
The word "commendam" is the accusative singular of the Low Latin noun commenda, "trust", or "custody", which is derived from the verb commendare ("to entrust").
Granting a benefice in commendam became most common with monasteries, and the commendatory abbot drew a portion of the revenue of the monastery but without fulfilling the duties of the abbot or even residing at the monastery.
The establishment of eccelsiastical benefices was a way of guaranteeing the financial stability of the Church. Real property and other goods donated to the Church were erected as a stable fund, and the revenue was attached to a particular office. The parish priest, bishop, or other minister would have the right to receive the income of the benefice to support himself and to cover the expenses related to his ministry.
There is clear evidence that the granting of a benefice in commendam was practiced in the fourth century. In a letter Ambrose mentions a church which he gave in commendam, while he was Bishop of Milan: "Commendo tibi, fili, Ecclesiam quae est ad Forum Cornelii... donec ei ordinetur episcopus" (Epistle ii) ("I entrust unto thee, my son, the church which is at the Cornelian Forum ... while [the bishop is allotted to it]").
Temporarily unoccupied church property (ecclesiastical benefice) could be entrusted to the protection of a member of the church, to safeguard and manage it until order was restored and a new permanent holder of the position was granted in titulum. The patron would receive any revenues generated from the property in the meantime. Each of the early basilicas of Rome was under the guardianship of a patron.