Thank you for the question on testing of faith, “If Abraham and Job lived at approximately the same time, why didn’t God choose the former as his example of faith to Lucifer instead of Job?”
As I reflected on the question, the test of faith is not to Lucifer nor to Job, but the accusation was against God. Satan accused God of “buying” Job’s loyalty to God. Satan was almost certain that if God withdrew his blessings or protections that Job would betray or even disowned God. Job’s wife did as she asked him to just curse God and then die. The attack by Satan was on God.
As to the question on why God didn’t God highlighted Abraham instead of Job is unknown. Here are some thoughts as to the possible reasons why God didn’t choose Abraham over Job:
A. Abraham wasn’t as wealthy in comparison to Job. For most of Abraham’s life, he was a nomad traveling from place to place. Job was established as he had a home and a very sizeable possession of animals and servants. Job had more to lose, if I may use that term, than Abraham. Job’s poverty would be deeper and broader (Job 1:3).
B. Abraham had two children in his old age. He had two sons: Ishmael and Isaac without mentioning any daughters. Job had seven sons and three daughters at the prime of his life. Job had more to lose than Abraham since he had 10 children. Job’s grief would be much deeper and broader (Job 1:2).
C. Abraham’s physical age in comparison to Job’s physical suffering would be incomparable. Abraham felt emotional pain of not having an heir for decades while Job felt both intense physical illnesses constantly. Job’s physical suffering was unbearable in that he wished that he was born. Job’s physical suffering was was much deeper and broader. (Job 3:1–26).
D. Abraham did not have family or friends accusing him of hidden sins, but Job had three friends who accused him of hidden sins. Abraham didn’t faced verbal abuse but Job did again and again in their rounds of conversation. Job’s moral character was questioned much more than Abraham.
E. Abraham had God speaking to him throughout his life while Job did not hear God’s voice until the end of his trial. Abraham had God’s promises of blessings in Gen. 12:1–3 to rely upon, while Job didn’t have any divine revelation until the fourth friend share his thoughts (Job 38:1). Abraham had answers from God, but Job didn’t even know why he had to go endure all his sufferings.
Abraham was kept in the “light” of what was happening to him, while Job was kept in the “dark” of what was happening to him.
SUMMARY: Satan knew that he couldn’t touch Abraham since God already promised to bless and protect him, but that wasn’t given to Job. Satan would have been limited to what he can do to Abraham, but not to Job.
For more discussion: