There's a famous teaching from Niddah 30b that a baby is taught the entire Torah in utero.
Someone once referenced this gemara and asked The Rav, if that's the case why don't we stand for a pregnant woman whenever she enters a room- aren't we supposed to stand for someone (ie the unborn baby) who knows kol HaTorah kula?
To which The Rav responded, that's not Torah that was acquired by "עמילות" i.e. "exerting oneself."
Anyone know the source for where I can find this teaching?