John Gill Commentary Romans 4:23

"Now it was not written for his sake alone, that it was reckoned unto him;" — Romans 4:23 (ASV)

Now it was not written for his sake alone
This was not left on the sacred records, (Genesis 15:6),

that it was imputed to him;
purely on his account, merely for his sake, as an encomium of his faith, and an honourable testimony to it, and for the encouragement of it; though this was doing him a very great honour, and was one design of it.