Then the Eternal One said to Moses, "Go to Pharaoh. For I have hardened his heart and the hearts of his courtiers, in order that I may display these My signs among them." - Exodus 10:1
Now when Pharaoh let the people go, God did not lead them by way of the land of the Philistines, although it was nearer; for God said, "The people may have a change of heart when they see war, and return to Egypt." - Exodus 13:17
Tu BiShvat or the "New Year of the Trees" is Jewish Arbor Day. The holiday is observed on the 15th (tu) of the Hebrew month of Shvat.