Baltimore Catechism No. 3
Q. 792. What should we do if we cannot remember the number of our sins?
A. If we cannot remember the number of our sins, we should tell the number as nearly as possible, and say how often we may have sinned in a day, a week, or a month, and how long the habit or practice has lasted.
Q. 793. Is our Confession worthy if, without our fault, we forget to confess a mortal sin?
A. If without our fault we forget to confess a mortal sin, our Confession is worthy, and the sin is forgiven; but it must be told in Confession if it again comes to our mind.
Q. 794. May a person who has forgotten to tell a mortal sin in confession go to Holy Communion before going again to confession?
A. A person who has forgotten to tell a mortal sin in confession may go to communion before again going to confession, because the forgotten sin was forgiven with those confessed, and the confession was good and worthy.
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