Obligation by the Black Friars to say a Mass for the souls of Mathew Stewart Laird of Castlemilk and for the souls of his mother and his children, in exchange of a payment of 10 merks annually to the prior and covenant, and if the heirs of said Matthew continue to found an annual rent of 20 shillings perpetually to the said convent of Glasgow, then the Mass shall be changed into a song Mass.