、。
The reason why God allows Satan to do such things is explained in the Book of Job in the Bible.
Literal
Satan [genitive-の] such-kind-of deeds [object-を] God [subject-が] why is-permitting [nominalizer-のか], that reason [topic-は] Bible [genitive-の] Book of Job [at-で] is-being-explained.
A religious-studies sentence. The structure is a fronted wh-question that then becomes the topic of the main clause: [why question]のか、その理由は[explained in Y]. The fronting is a kind of left-dislocation, setting up 'the question of why X' and then telling you where the answer is. The nested verb 許している is the ~ている resultative of 許す ('allow, forgive') — 'is allowing (as an ongoing state).' サタン (Satan) and ヨブ記 (the Book of Job) are Biblical proper nouns. 聖書 is the standard word for 'the Bible' or 'holy scriptures.'