What is the role of “ghayra mufsidihā” in the rain-prayer example?

Iṭnāb: Tadhyīl, Takmīl (Iḥtirās), and Tatmīm

• It excludes destructive rain from the intended wish
• It denies that any rain will fall
• It denies the existence of dwellings
• It turns the wish into an ordinary past-tense report