Chasidut על שמות 3:19

Furthermore, the expression ‎היד הגדולה‎, instead of ‎היד ‏החזקה‎, “the strong, powerful hand,” is what we would ‎have expected, seeing that G’d had told Moses already ‎in Exodus 3,19 that Pharaoh would not release the ‎Israelites until He would intervene with ‎יד חזקה‎, “a ‎strong hand.” In light of our exegesis there is no ‎problem with these verses. G’d performed a great act ‎of loving kindness for the Egyptians who had been ‎allowed to serve as G’d’s instrument to induce faith in ‎the Lord by both the Israelites, and many gentiles who ‎heard about what had transpired at the sea of reeds. ‎‎[Compare Rahav in Joshua 2,9. Ed.] ‎This is what happened at the sea. On the other hand, in ‎Egypt, G’d had used ‎יד חזקה‎, “a strong hand,” i.e. the ‎attribute of Justice in order to discipline the Egyptians. ‎The true sanctification of G’d’s name occurred at the ‎sea of reeds, where His “great” name was sanctified, ‎hence the reference to ‎היד הגדולה‎, instead of ‎היד החזקה‎.‎
When someone has attained an advanced level in ‎his spiritual development, he has no need to watch ‎miracles as proof of G’d’s power in order to strengthen ‎his faith in Him as we have explained on previous ‎occasions. Anyone who possesses an average amount ‎of intelligence is aware of the existence of a Creator ‎who has created this universe. Only people of less than ‎average intelligence require miracles to bring home to ‎them that there is a Creator, who, seeing that the ‎universe is His, is able to wreak havoc with laws of ‎nature, i.e. laws which He Himself had established.‎