Reference for Bava Kamma 109:8

וכן חיה ועוף כיוצא בהן וכו': אמר ר"ל כאן שנה רבי תרנגול טווס ופסיוני כלאים זה בזה

— The real reason is that Scripture used this letter on the very first occasion to express something good, for from the beginning of Genesis up to [the verse] <i>And God saw the light</i><span class="x" onmousemove="('comment',' Gen. I, 4. ');">¹⁵</span> no <i>teth</i> occurs.<span class="x" onmousemove="('comment',' And since the first teth in Scriptures commences the word denoting 'good' it is a good omen to see it in a dream. ');">¹⁶</span>

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