I was hit because of the letter seen…

أن كاتب  عمرو بن العاص كتب إلى عمر فكتب: بسم الله , ولم يكتب السين, فكتب عمر إلى عمرو: أن اضربه سوطا, فضربه عمرو, فقيل له: في أي شيء ضربك؟ قال: في سين

مناقب أمير المؤمنين لابن الجوزي

Ibn alJawzi relates in his manaaqib ameer almumineen, that the scribe of Amr bil aas wrote to Umar and wrote bismAllah but omitted the letter seen. So Umar wrote back to Amr saying:  “Lash him once with the whip.” And Amr did so. The scribe was then asked: “In what matter were you hit?” He said, ‘ Because of the letter seen.