The very first word of the megilla, Eicha, which we read of 9 Av, recalls our patriarch Avraham (Abraham). According to the great commentator Me'am Lo'ez, citing another perspective: Eicha can be broken into two words - אי כה - Ei Cho - Where is Cho (thus)?
Hashem had promised Avraham, " כֹּה יִהְיֶה זַרְעֶךָ " Thus shall your seed be! (As many as the stars in the heavens!)
Therefore, when the prophet Jeremiah sees the downfall and destruction of the once lofty Jewish nation and the Holy Temple, he asks, "Where is that promise of Cho - thus shall your seed be?"
Hashem answers with His own question, Where is Cho?
G-d had commanded Moses, Cho, כֹּה תֹאמַר לְבֵית יַעֲקֹב , Thus you will tell the House of Jacob!
And now Hashem asks, "Where is the Nation that upholds Cho - G-d's mitzvot (commandments)?"
Friends, we have the opportunity to bring the Cho back by setting an example of blessing. When we keep Hashem's mitzvot and when we follow Avraham Avinu's teachings and ways of loving kindness, then Hashem's words to our Patriarch will be fulfilled.
Cho, thus shall your seed be - like the stars of the heavens.
May your Tisha B'Av conclude with meaning. May the joy of Tu B'Av follow with true joy and bracha (blessing) for Am Yisrael.