1)
What is the grammatical form of "Yira'ucha"?
1.
Radak: The Yud is for the future conjugation; the Yud of the root (Yarei, fear) is omitted.
2)
What will cause them to fear Hashem?
1.
Radak: When they see that You forgive them when they return to You and pray to You in this house, they will know that the plague or illness came due to their sin; it is not chance. Due to this they will fear You. The same applies to "Ki Imcha ha'Selichah Lema'an Tivarei" (Tehilim 130:4).
