[Avodah] Rav Yechiel Yaakov Weinberg: Davening in English?

[Simon Montagu]

On Tue, Sep 20, 2011 at 2:21 PM, Prof. Levine <llevine at stevens.edu> wrote:
> From http://revach.net/article.php?id=2324
>
> In 1954 a Rov in New York sent a question to Rav Yechiel Yaakov Weinberg the
> Baal Sridei Eish in Montreaux, Switzerland.  He wanted to know if it was
> permissible to allow saying the “Mizmorim” from davening in English as a
> congregation.
>
> The Sridei Eish (OC 9) answered that the question is a very sensitive one.

I looked at this teshuva inside, and could use some help in following
up a reference. The SE says "ויפה ביאר הגה"ק בעל ד"ח ח"ש סי' י"ח,
שעיקר דתנו מיוסד  על תורה שבע"פ ומסורת אבות, כמש"כ: שאל אביך ויגדך
וגו'‏". -- "Veyafe bi'er [he gimel he kuf = haga'on hakadosh??] ba`al
[dalet het = ?????] [het shin = helek sheni??] [samech yud, yud het =
siman 18] she`ikar datenu meyussad al tora sheba`al pe umesoret avot
kemo shekatuv 'she'al avicha veyagedcha ..."

Can someone help me identify the source quoted here? "Dalet Het" could
be almost anything.