احْفَظِ اللَّهَ يَحْفَظْكَ
“Observe Allah's commands; He will protect you.”
احْفَظْ is an imperative from the root ḥ-f-ẓ. In يَحْفَظْكَ, the attached كَ means “you.” A duty is stated first, followed by the promise of Allah's care.
This does not imply that a faithful person will never experience illness, loss or tests. Allah's protection may include safeguarding faith, granting guidance and helping through difficulty.
Example
Refusing to cheat when an opportunity arises is one way of observing Allah's limits, regardless of how the exam result turns out.