The expression “his blood shall be upon his (our) head” (see Revised Standard Version) is a way of saying “he (we) will be responsible for that person’s death.” Every member of Rahab’s family will be safe during the attack on Jericho so long as he or she stays in Rahab’s house; and, in fact, they were all spared (see verses 6.23 and 6.25). His death will be his own fault may be restructured as either “he will be killed, and it will be his own fault” or “we will kill him, and….” The spies are affirming that everyone except the persons found in Rahab’s house will be put to death.

Quoted with permission from Bratcher, Robert G. and Newman, Barclay M. A Handbook on Joshua. (UBS Helps for Translators). New York: UBS, 1983. For this and other handbooks for translators see here .