‘…Honoured sir, I ask you to discontinue those Masses and vigils and daily prayers for her soul. It is enough to pray God once or twice for her, because he has said to us, ‘Whatsoever ye shall ask, if ye believe, ye shall receive.’ If we keep on praying for the same thing, it is a sign that we do not believe, and we only annoy him with our unbelieving prayers. For what does it mean if I repeatedly pray for the same thing except that my earlier prayers were not answered and that I have prayed contrary to his will? It is true that we ought to pray at all times, but we should do so in faith, certain that we are heard, otherwise the prayer is in vain. And we are never at a loss for something new to pray for.’
–Luther: Letters of Spiritual Counsel, ed. by Theodore G Tappert (Regent College Publishing: Vancouver, BC; 1960)