What is the ruling on someone who commits a sin and intends to repent by saying, "I will repent from it, God willing"?

A Muslim must hasten to immediate repentance from all sins, for delaying repentance is another sin that necessitates repentance. One who procrastinates repentance is in great danger, for he has no guarantee of survival. Moreover, delaying repentance increases its difficulty, as sin becomes more deeply rooted with habit, and a person's weakness increases. Therefore, repentance should not be postponed.