From my archives.....
In the Hagada [and in Shachris on Shabbos morning] we talk about the greatness of the songs of Dovid and then go into Yishtabach where we say הבוחר בשירי זמרה - He chooses the songs [of Dovid]. Tehillim is a very special sefer. It begins with the words אשרי מי שלא הלך בעצת רשעים - Fortunate is he who didn't go in the path of the reshaim. Chazal say that this refers to Avraham who didn't follow in the path of the Dor Haflaga [the generation of the "Tower of Babylon". Take the train to Babylon and switch at Jamaica!].
Why does Tehillim start with a reference to the refusal of Avraham to join the rebellion, such a vague, unknown event in history? It is very nice that Avraham didn't follow those who rebelled against Hashem but why does that appear at the beginning of tehillim?
In Hagadas Marbeh Li-sappeir, it is explained that the punishment of the Dor Haflaga was the mixing up of their languages. Avraham, who refused to join them, was rewarded with a very special and uniquely powerful lashon. Dovid begins tehillim and tells us that his כח הלשון is drawn from Avraham Avinu! הבוחר בשירי זמרה - Hashem chooses these special songs.
In that first perek it says ועלהו לא יבול which Chazal understand to mean that even the mundane speech of talmidei chachomim requires limmud because it contains depth. This pasuk appears here because this is the perek which glorifies the power of speech of those who don't go בעצת רשעים and all of their interest is in Torah - בתורת השם חפצו ובתורתו יהגה יומם ולילה.
We may add that Chazal say that Avraham Avinu had a gem on his neck and every sick person who saw it was healed. Rabbeinu Bechaye [hakdama to Yisro] says that this "gem" was his כח הדיבור. He could heal people with his powerful speech.
Many times we have discussed the two covenants Hashem makes with us - ברית הלשון and ברית המעור. The second bris, מעור, meaning bris milah, is famous. Now we have an expression of the first bris - the ברית הלשון Hashem made with Avraham Avinu.
It is also fascinating to add what we discussed elsewhere in a different context - that Dovid was both the father of Moshiach and the author of tehillim. The poetry in tehillim is a harbinger of the end of days. The vision of the future is expressed by the navi כי אז אהפוך אל עמים שפה ברורה לקרוא כולם בשם השם - All of the nations will have a "clear speech" to call in the name of Hashem. There will be a tikkun of the power of speech. The source is the positive, healing speech of Avraham Avinu.
The process of tikkun ha-dibbur begins with Avraham Avinu and will conclude at the end of days. It is obvious from here that Dovid, the antecedent of Moshiach, felt compelled to begin his sefer of eschatological [end of days] poetry with a reference to כח הדיבור of Avraham Avinu.
On Pesach, the night of speech פה סח [speaking mouth], the gemara says that we must begin with the words מתחילה עובדי עבודה זרה היו אבותינו ועכשיו קרבנו המקום לעבודתו - At the beginning we were idolaters but now Hashem has brought us close to His avoda. Who was is the "idolater" to whom we refer? Some say that we refer to Avraham [Terach is not "Avoseinu"]. He started out as an idolater but afterwards he came close to the "avoda" of Hashem. "Avoda" [according to Chazal] is a euphemism for tfilla - and less famously, but cited in the name of Chazal by the Rambam in Sefer Hamitzvos - Torah. Both are performed with SPEECH. We begin the hagada with an emphasis on the tikkun of speech and we conclude the hagada with חד גדיא which of course is a reference to the end of days when Hashem will slaughter the angel of death! When someone is shechted it is done on the place from where speech emanates [known in English as a "throat"]. Just as we find that the dor haflaga was punished with a mixing up of their speech and concomitantly Avraham was given a special speech, so at the end of days, the power of speech of evil [הוא שטן הוא יצר הרע הוא מלאך המוות - יורד ומשטין עולה ומקטרג נוטל רשות ונוטל נשמה - עי' בב"ב ט"ז] will be liquidated and we will be zoche to the tikkun ha-shalem of pure speech!
כימי צאתך מארץ מצרים אראנו נפלאות - Geulas Mitzraim was the root of the ultimate geula. May we fix our speech and merit to see the redemption speedily in our days!