Adam Clarke

Now therefore let me alone - Moses had already begun to plead with God in the behalf of this rebellious and ungrateful people; and so powerful was his intercession that even the Omnipotent represents himself as incapable of doing any thing in the way of judgment, unless his creature desisted from praying for mercy! See an instance of the prevalence of fervent intercession in the case of Abraham, Gen 18:23-33, from the model of which the intercession of Moses seems to have been formed.