When will Yisrael seek Hashem?
Rashi: After the days of Galus.
Radak: It will be in the end of days, close to the time of salvation; Yisrael will repent.
What is the significance of seeking Hashem and David, and fearing Hashem and his good?
Rashi citing Midrash Shmuel 13:4: Yisrael despised three things in the days of Rechav'am ? Malchus Shamayim, Malchus Beis David and the Beis ha'Mikdash. "Mah Lanu Chelek b'David" (Melachim I, 12:16) is like the simple meaning; we read "l'Ohalecha" (ibid.) like lEi'lokecha; "Re'eh Beisecha David" (ibid.) is the Beis ha'Mikdash. Yisrael will not see a good sign (Radak ? a sign of Ge'ulah) until they return to request all three. "U'Vikshu Es Hashem" is Malchus Shamayim; "v'Es David Malkam" is like the simple meaning; "u'Fachadu El Hashem v'El Tuvo" is the Beis ha'Mikdash ? "ha'Har ha'Tov ha'Zeh" (Devarim 3:25).
Radak citing Targum Yonasan: Yisrael will seek Avodas Hashem, [heed Mashi'ach ben David, and gather to serve Him. They will have great good in the end of days!]
Why does it say "u'Fachadu El Hashem v'El Tuvo"?
Radak: They will fear Hashem when they return to Him. With Teshuvah, they will hope for the great good that He promised to them.
Radak citing Rav Sadya Gaon: Tuvo is His honor, like "Ani A'avir Kol Tuvi Al Panecha" (Shemos 33:18).
Malbim: They will fear then, for He will return His good and Shechinah in Tziyon, i.e. the Beis ha'Mikdash, and dwell among them. This will be at the end. Yisrael were commanded to appoint a king, eradicate the seed of Amalek, and afterwards build the Beis ha'Mikdash (Sanhedrin 20b). Appointing a king is the crown of kingship; eradicating Amalek will make Hashem's name complete (refer to 3:2:2:8*), and Beis David on Kisei Hashem in the kingship of Shamayim and Aretz. Then, the crown of Torah will be complete. There will be a king, telling the future via Ru'ach ha'Kodesh which is the power of Hashem's name, and then building the Beis ha'Mikdash, which is the Zevach and the crown of Kehunah.
