Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

In conclusion, the spies guarded against any arbitrary interpretation and application of their oath, by imposing three conditions, on the non-fulfilment of which they would be released from their oath. הזּה for הזּאת is to be explained in Jos 2:17 from the fact that the gender is often disregarded in the use of the pronoun (see Ewald, 183, a.), and in Jos 2:18 from the fact that there the gender is determined by the nomen rectum (see Ewald, 317, d.). Jos 2:18 The first condition was, that when the town was taken Rahab should make her house known to the Israelites, by binding "the cord of this crimson thread," i.e., this cord made of crimson thread, in the window from which she had let them down. The demonstrative "this" leads to the conclusion adopted by Luther and others, that "this cord" is the rope (חבל) mentioned in Jos 2:15, as no other word had been mentioned to which they could refer; and the fact that nothing has been said about the sign in question being either given or received, precludes the idea that the spies gave the cord to Rahab for a sign. The crimson or scarlet colour of the cord (שׁני = שׁני תּולעת; see at Exo 25:4), as the colour of vigorous life, made this cord an expressive sign of the preservation of Rahab's life and the lives of her relations. The second condition was, that when the town was taken, Rahab should collect together her parents, and her brothers and her sisters, into her own house. 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).