Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

And so also the man who hit another in hatred, or threw at him by lying in wait, or struck him with the hand in enmity, so that he died. And if a murderer of this kind fled into a free city, the elders of his city were to have him fetched out and delivered up to the avenger of blood (Deu 19:11-12). Then follow, in Num 35:22-28, the proceedings to be taken with an unintentional manslayer, viz., if any one hit another "in the moment," i.e., suddenly, unawares (Num 6:9), without enmity, or by throwing anything upon him, without lying in wait, or by letting a stone, by which a man might be killed, fall upon him without seeing him, so that he died in consequence, but without being his enemy, or watching to do him harm. In using the expression בּכל־אבן, the writer had probably השׁליך still in his mind; but he dropped this word, and wrote ויּפּל in the form of a fresh sentence. The thing intended is explained still more clearly in Deu 19:4-5. Instead of בּפתע, we find there בּבלי־דעת, without knowing unintentionally. The words, "without being his enemy," are paraphrased there by, "without hating him from yesterday and the day before yesterday" (i.e., previously), and are explained by an example taken from the life: "When a man goeth into the wood with his neighbour to hew wood, and his hand fetcheth a stroke with the axe to cut down the tree, and the iron slippeth (נשׁל Niphal of שׁלל) from the wood (handle), and lighteth upon his neighbour."