Heavy spoilers for those who didn't see the last episode of Season 10.
During this episode
The Doctor is fighting not to regenerate.
We can see that in the end of the episode, but also in the middle.
But at then end of the episode
The Doctor quotes number 10 and number 11 regeneration phrases : "I don't wanna go" and "Remember when the doctor was me".
But moreover we learn afterwards that
One of the earlier quotes was actually from his first incarnation : "The Original you might say".
This realisation makes me think that
the impending regeneration is blurring the lines between number 12 and previous Doctors, thus leading to these quotes resurfacing.
But this might be the case during all of the episode. And not only in the end.
My question is : Are there any other direct quotes from previous incarnations of the doctor in this episode ?
PS : I willingly did not use the tag "regeneration" since the question title mentions the episode. The tag should be here, but would create a spoiler.