The answer
"He" is referring to the one witnessing his brother committing the "sin"."Him" is referring to the brother that is sinning.
The Holy Bible (NKJV) titles this passage "Confidence and Compassion in Prayer". When we witness other believers straying; we ought to pray for them, believing with all confidence that God can and will intervene because it is His will that all should repent and return to Him. Either physical death prior to repentance; or spiritual death because of blasphemy against the Holy Spirit through refusal to repent or to believe, qualifies as the abysmal and inexcusable sin, the sin leading to death. The sin not leading to death is the repented sin. In this regard, we are required to pray for each other, earnestly and confidently, for the safe return of our brethren who have gone astray.
"For you were like sheep going astray, but have now returned to the Shepherd and Overseer of your souls" (1 Peter 2:25).
Answered by His Eminence Metropolitan Youssef (opens in a new tab)