Reference for Negaim 13:11

מְצֹרָע שֶׁנִּכְנַס לְבַיִת, כָּל הַכֵּלִים שֶׁיֶּשׁ שָׁם טְמֵאִין, אֲפִלּוּ עַד הַקּוֹרוֹת. רַבִּי שִׁמְעוֹן אוֹמֵר, עַד אַרְבַּע אַמּוֹת. כֵּלִים, מִיָּד טְמֵאִין. רַבִּי יְהוּדָה אוֹמֵר, אִם שָׁהָה כְדֵי הַדְלָקַת הַנֵּר:

A leper who enters a house, all of the vessels within it become impure even up to the beams. Rabbi Shimon says, [only] up to four cubits. The vessels become impure immediately. Rabbi Yehuda says, not until he stays long enough to light a candle.

Jastrow