Bava Kamma 60A

סלתא, שרגא, דההוא ודאי מעשה דידיה גרמו.

of thin wood and a candle [sheraga], since in that case his own action, i.e., that of the one who sent the flame, definitely caused the fire to spread.

שלח ביד פקח ⁠– הפקח חייב וכו׳. אמר רב נחמן בר יצחק: מאן דתני ״ליבה״ לא משתבש, ומאן דתני ״ניבה״ לא משתבש.

The Mishnah teaches that if one sent a fire in the hand of a halakhically competent person, the halakhically competent person is liable…If another came and fanned the flame the one who fanned it is liable. Rav Naḥman bar Yitzḥak says with regard to the correct text of the Mishnah: The one who teaches it using the word fanned [libba] is not mistaken, and the one who teaches it using the word blew [nibba] is not mistaken.

מאן דתני ״ליבה״ לא משתבש ⁠– דכתיב: ״בלבת אש״. ומאן דתני ״ניבה״ לא משתבש ⁠– דכתיב: ״בורא ניב שפתים״.

Rav Naḥman explained: The one who teaches using the word fanned [libba] is not mistaken, as it is written: “With a flame [belabbat] of fire” (Exodus 3:2), and the one who teaches using the word blew [nibba] is not mistaken, as it is written: “He creates the fruit [niv] of the lips” (Isaiah 57:19), which can be interpreted as referring to the breath of the lips.

לבתה הרוח ⁠– כולן פטורין. תנו רבנן: ליבה ולבתה הרוח, אם יש בלבויו כדי ללבותה ⁠– חייב, ואם לאו ⁠– פטור.

§ The Mishnah teaches: If the wind fanned the flames, all the people involved are exempt, indicating that even if one fanned the fire at the same time that the wind was blowing he is exempt. The Talmud cites a baraita in which A baraita states the same idea explicitly: In a case where one fanned the flame and at the same time the wind fanned it, if his fanning has sufficient strength by itself to fan the flames, he is liable for damage caused by the fire, since even without the wind the fire would have spread. But if his fanning alone was not sufficient, he is exempt.