Translation:

98. When thou dost read the Qur'an seek Allah's protection from Satan the rejected one.

Notes (Tafseer)

2139. Evil has no authority or influence on those who put their trust in Allah. It is good to express that trust in outward actions, and a formal expression of it-as in the formula, "I seek Allah's protection from Evil"-helps us. Man is weak at best, and he should seek strength for his will in Allah's help and protection.