Does applying oil into the urethra invalidate the fast?
General Chapter
Al-Mughni
Book of Fasting
Primary text
Applying oil into the urethra does not invalidate the fast, whether it reaches the bladder or not. This is the position held by Abu Hanifa. The evidence is that there is no direct passage between the interior of the urethra and the internal cavity (jawf). The urine exits the urethra only by seepage, so what remains in the urethra does not reach the interior cavity, and thus does not break the fast, analogous to applying something to the mouth that is not swallowed.
Supporting text
Imam Al-Shafi'i holds that applying oil into the urethra invalidates the fast because it introduces a substance into an internal cavity of the body, similar to a wound penetration (ja'ifah). Furthermore, since semen exiting the penis invalidates the fast, what enters through the opening from which semen exits should also be a cause for invalidation, just as the mouth is considered an entry point.