Source and decoding - Bava Batra 2b
טַעְמָא דְּרָצוּ, הָא לֹא רָצוּ – אֵין מְחַיְּיבִין אוֹתוֹ; אַלְמָא הֶיזֵּק רְאִיָּה לָאו שְׁמֵיהּ הֶיזֵּק.
The Gemara infers: the reason is that they wished - had they not wished, he is not compelled.
The Gemara infers: the reason is that they wished - had they not wished, he is not compelled. If building happens only by wish, there seems to be no duty, suggesting: damage by sight is not called damage. The Gemara will test this inference and propose other readings of "partition."