Commentary for Berakhot 66:17

<big><strong>גמ׳</strong></big> בשלמא מודים מודים משתקין אותו משום דמיחזי כשתי רשויות ועל טוב יזכר שמך נמי משמע על הטובה ולא על הרעה ותנן חייב אדם לברך על הרעה כשם שמברך על הטובה אלא על קן צפור יגיעו רחמיך מ"ט

GEMARA It is right that we silence him who says, "We give thanks, we give thanks," because he makes it appear as though there were two Powers; and likewise him who says, "For the good be Thy name remembered," the inference being that for the good [may it be remembered] but not for the bad ; and we have a Mishnaic teaching : A man is in duty bound to utter a benediction for the bad even as he utters one for the good. But why [do we silence him who says], "To a bird's nest do Thy mercies extend"?

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot