As early as the time of Constantine I, especial insistence was put upon the obligation to hear Mass on Sundays and Holy Days, to receive the sacraments and to abstain from contracting marriage at certain seasons. In the seventh-century Penitentiary of Theodore of Canterbury we find penalties imposed on those who contemn the Sunday and fail to keep the fasts of the Church as well as legislation regarding the reception of the Eucharist. In the sixteenth century Martin Aspilcueta(1586), gives a list of five principal precepts of obligation: