The transition is abrupt from the promise of triumph over Pharaoh to the threat of instant death. But we must bear in mind that some days may have elapsed between the two, and that the sin which provoked the menace was probably not committed at the date of the promise.
The narrative of Exodus 4:24-26 is obscure from its brevity; but the most probable explanation of the circumstances is, that Zipporah had been delivered of her second son, Eliezer, some few days before she set out on the journey to Egypt.
Childbirth, it must be remembered, in the East does not incapacitate a person from exertion for more than a day or two. On the journey, the eighth day from the birth of the child arrived, and his circumcision ought to have taken place; but Zipporah had a repugnance to the rite, and deferred it, Moses weakly consenting to the illegality.
At the close of the eighth day, when Moses went to rest for the night, he was seized with a sudden and dangerous illness, which he regarded, and rightly regarded, as a God-inflicted punishment, sent to chastise his sin in breaking the Divine command (Genesis 17:10-12).
Zipporah understood the matter in the same way; and, as her husband was too ill to perform the rite, she herself with her own hand cut off her boy's foreskin, and, still indignant at what she had been forced to do, east it at her husband's feet, with the reproach—"Surely a bloody husband art thou to me."
The rite once performed, however reluctantly, God remitted his anger, and. allowed Moses to recover his health, and pursue his journey.