C. F. Keil and Franz Delitzsch on Joshua 2:19-20

Jos 2:19-20

Whoever went outside the door, his blood should be upon his own head; i.e., if he was slain outside by the Israelitish soldiers, he should bear his death as his own fault. But every one who was with her in the house, his blood should fall upon their (the spies') head, if any hand was against them, i.e., touched them or did them harm (vid., Exo 9:3). The formula, “his blood be upon his head,” is synonymous with the legal formula, “his blood be upon him” (Lev 20:9). The third condition (Jos 2:20) is simply a repetition of the principal condition laid down at the very outset (Jos 2:14).