The LORD knew that Pha'raoh was not speaking the truth when he promised to let the Is'ra-el-ites go, but He told Mo'ses to deal kindly with any acts which seemed to show repentance on the part of the king. He had already shown great mercy and forgiveness toward Pha'raoh, and did not let him pay the penalty for his evil ways until the last possible offer of mercy had been scorned.
The soul of man is so constituted that the continued rejection of the mercies of God leaves it less ready to yield to them. The abuse of Divine Grace has a hardening effect upon man's moral nature. Pha'raoh had paid no attention to repeated offers of mercy, and had not learnt wisdom from continued acts of Divine Justice. But he was not yet wholly forsaken by God, and still further opportunities were given him to prove that his repentance was genuine.
Mo'ses and Aa'ron had called upon Him before and after each plague, and He had shown mercy toward him whenever it was asked. Under the influence of these repeated acts of grace the heart of the king must either melt into genuine repentance or harden into an even more obstinate state. To say that God hardened Pha'raoh's heart means only that the LORD continued to test the king until it was clear that he definitely preferred the ways of evil to those of good. The Lord did not force Pha'raoh to choose either course, He merely left him in freedom to follow the desires of his own heart
"Till, like a frozen mass, his heart was chilled,
Its upward movement stayed, and conscience stilled."
Mo'ses was generous and forbearing toward the wicked king in his confessions of guilt, in his acknowledgment of the righteousness of God, and in his request for pardon. Nevertheless, Mo'ses reminded the king that he had little confidence in the truth of his words, and fearlessly told him that his repentance was not real. He promised, however, to ask the LORD to put an end to the rain and hail and lightning. Mo'ses then went outside the city, raised his hands toward Heaven in a prayer to God, and the terrible storm ceased at once.
Once again Pha'raoh failed to keep his promise. He took back his permission for the Is'ra-el-ites to leave E'gypt, and turnt against the LORD as wickedly as before.
Now that the seventh plague had failed to produce any real change in the attitude of Pha'raoh toward the requests of Mo'ses and Aa'ron, the LORD sent his servants to deliver a strong message to the king, and to announce that a much greater plague was coming.
