Exodus 3:19

לא יתן אתכם מלך מצרים להלך THE KING OF EGYPT WILL NOT LET YOU GO, if I do not (ולא) show him My strong hand (יד חזקה) — it is as much as to say: so long as I do not let him feel My strong hand he will not let you go. לא יתן — Translate this as the Targum does: he will not give leave. Similar uses of נתן followed by ל with the infinitive in sense of permitting are: (Genesis 20:6) “therefore I did not permit thee (נתתיך) to touch her”; (Genesis 31:7) “And God did not permit him (נתנו) to do me evil”. Still all these passages really have the sense of giving”. Some explain the phrase ולא ביד חזקה to signify: “He will not permit you to go, and this will not be because his hand is strong”, for (v. 20) “As soon as I stretch forth My hand I will smite the Egyptians [… and afterwards he will let you go]”. And so the Targum renders it: and not on account that his power is mighty. This explanation was told me in the name of Rabbi Jacob the son of Menachem.

וַאֲנִ֣י יָדַ֔עְתִּי כִּ֠י לֹֽא־יִתֵּ֥ן אֶתְכֶ֛ם מֶ֥לֶךְ מִצְרַ֖יִם לַהֲלֹ֑ךְ וְלֹ֖א בְּיָ֥ד חֲזָקָֽה׃

And I know that the king of Miżrayim will not let you go, if not by a mighty hand.