Rashi on Deuteronomy 19:5/רש"י על דברים י״ט:ה׳

1ונדחה ידו AND HIS HAND MOVED (SLIPPED) when he was about to let the axe fall upon the tree. The Targum rendering is ותתמריג ידה, the meaning being, “his hand moved itself to let the stroke of the axe fall upon the tree”. The words (II Samuel 6:6) כי שמטו הבקר are rendered in Targum Jonathan on by: ארי מרגוהי תוריא “for the oxen moved it (the Ark)”

2ונשל הברזל מן העץ — Some of our Rabbis say that this means that the iron (axe) flew off from its handle (העץ); but some of them say that it means that the iron made a splinter of wood fall off from the tree which was being chopped, and it sprang off and killed him (according to this explanation the word העץ in both cases refers to the tree) (Makkot 7b).