Satan bet against Job in front of God in Job 1:
Because Satan wanted to use his wife to accomplish his bet:
Job 2:
Satan thought he could use his wife to get Job to curse God. Satan's plan failed.
God accepted the bet:11 "stretch out your hand and touch all that he has, and he will curse you to your face.”
Then Satan took Job’s property and killed his children, but he spared Job's wife. Why?12 And the LORD said to Satan, “Behold, all that he has is in your hand. Only against him do not stretch out your hand.” So Satan went out from the presence of the LORD.
Because Satan wanted to use his wife to accomplish his bet:
Job 2:
That was the pivotal moment that Satan was waiting for. Would Job do what his wife said and accomplish Satan's win? The answer was a resounding "no":9 Then his wife said to him, “Do you still hold fast your integrity? Curse God and die.”
Job rebuked his wife for saying such nonsense.10 But he said to her, “You speak as one of the foolish women would speak.
Why did Satan spare Job's wife?Shall we receive good from God, and shall we not receive evil?” In all this Job did not sin with his lips.
Satan thought he could use his wife to get Job to curse God. Satan's plan failed.