Exodus 9:2
"For if thou refuse to let them go, and wilt hold them still,"
Cross References (ranked by relevance)
And if thou refuse to let them go, behold, I will smite all thy borders with frogs:
And men were scorched with great heat, and blasphemed the name of God, which hath power over these plagues: and they repented not to give him glory.
But if ye refuse and rebel, ye shall be devoured with the sword: for the mouth of the LORD hath spoken it.
And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy firstborn.
But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath,
But God shall wound the head of his enemies, and the hairy scalp of such an one as goeth on still in his trespasses.
Else, if thou refuse to let my people go, behold, to morrow will I bring the locusts into thy coast: