"In the selfsame day, as God had said unto him." (Gen. 17:23)
Instant obedience is the only kind of obedience there is; delayed obedience is disobedience. Every time God calls us to any duty, He is offering to make a covenant with us; doing the duty is our part, and He will do His part in special blessing.
The only way we can obey is to obey "in the selfsame day," as Abraham did. To be sure, we often postpone a duty and then later on do it as fully as we can. It is better to do this than not to do it at all. But it is then, at the best, only a crippled, disfigured, half-way sort of duty-doing; and a postponed duty never can bring the full blessing that God intended, and that it would have brought if done at the earliest possible moment.
It is a pity to rob ourselves, along with robbing God and others, by procrastination. "In the selfsame day" is the Genesis way of saying, "Do it now." --Messages for the Morning Watch.
Luther says that "a true believer will crucify the question, 'Why?' He will obey without questioning." I will not be one of those who, except they see signs and wonders, will in no wise believe. I will obey without questioning.
"Ours not to make reply,
Ours not to reason why,
Ours but to do and die."
Obedience is the fruit of faith; patience, the bloom on the fruit. --Christina Rossetti.