'Severely' in the Bible

May God punish Abner and do so severely if I don’t do for David what the Lord swore to him:

Then they came to urge David to eat bread while it was still day, but David took an oath: “May God punish me and do so severely if I taste bread or anything else before sunset!”

And tell Amasa, ‘Aren’t you my flesh and blood? May God punish me and do so severely if you don’t become commander of the army from now on instead of Joab!’”