From the Council of Avranches, in Normandy, Legates of the Apostolic See Presiding, A.D. 1172

Canon X. Let a man not pass over to religion while his wife remains in the world, or conversely, unless both have passed beyond the time for being available to the works of the flesh.

The consent of both does not suffice, but the time also of advanced age is required. Frequent proneness to works of the flesh suggested this tempering to the Fathers.