When Pharaoh saw that there was respite. — Hebrew, a breathing space.
He hardened his heart. — Hitherto Pharaoh’s nature had not been impressed; his heart had remained dull, callous, hard. Now an impression had been made (Exodus 8:8), and he must have yielded, if he had not called in his own will to efface it. Herein was his great guilt. (See the comment on Exodus 4:21.)