Bava Kama1: 1
אַרְבָּעָה אֲבוֹת נְזִיקִים: הַשּׁוֹר, וְהַבּוֹר, וְהַמַּבְעֶה, וְהַהֶבְעֵר. לֹא הֲרֵי הַשּׁוֹר כַּהֲרֵי הַמַּבְעֶה, וְלֹא הֲרֵי הַמַּבְעֶה כַּהֲרֵי הַשּׁוֹר. וְלֹא זֶה וְזֶה, שֶׁיֵּשׁ בָּהֶן רוּחַ חַיִּים, כַּהֲרֵי הָאֵשׁ, שֶׁאֵין בּוֹ רוּחַ חַיִּים; וְלֹא זֶה וְזֶה, שֶׁדַּרְכָּן לֵילֵךְ וּלְהַזִּיק, כַּהֲרֵי הַבּוֹר, שֶׁאֵין דַּרְכּוֹ לֵילֵךְ וּלְהַזִּיק. הַצַּד הַשָּׁוֶה שֶׁבָּהֶן שֶׁדַּרְכָּן לְהַזִּיק, וּשְׁמִירָתָן עָלֶיךָ, וּכְשֶׁהִזִּיק, חָב הַמַּזִּיק לְשַׁלֵּם תַּשְׁלוּמֵי נֶזֶק בְּמֵיטַב הָאָרֶץ.
The four primary damagers are: the bull, the pit, the maveh, and the fire. The bull is not like the maveh, nor is the maveh like the bull. These two, which are living things, are not like the fire, which is not a living thing; nor are these, whose manner is to go forth and damage, like the pit, whose manner is not to go forth and damage. The common feature in them is that their manner is to damage, and you are responsible to watch them, and when it damages, the damager is obligated to pay for the damage with the best of the land.
Bava Kama1: 2
כֹּל שֶׁחַבְתִּי בִשְׁמִירָתוֹ הִכְשַׁרְתִּי אֶת נִזְקוֹ. הִכְשַׁרְתִּי בְמִקְצָת נִזְקוֹ, חַבְתִּי בְתַשְׁלוּמִין כְּהֶכְשֵׁר כָּל נִזְקוֹ.  נְכָסִים שֶׁאֵין בָּהֶן מְעִילָה, נְכָסִים שֶׁל בְּנֵי בְרִית, נְכָסִים הַמְיֻחָדִים, וּבְכָל מָקוֹם חוּץ מֵרְשׁוּת הַמְיֻחֶדֶת לַמַּזִּיק וּרְשׁוּת הַנִּזָּק וְהַמַּזִּיק. וּכְשֶׁהִזִּיק, חָב הַמַּזִּיק לְשַׁלֵּם תַּשְׁלוּמֵי נֶזֶק בְּמֵיטַב הָאָרֶץ.
Anything that I am obligated to watch I have perpetrated its damage. [If] I partially perpetrated its damage, I am obligated to pay as though I had completely perpetrated its damage.  [The law of damages applies to] property that is not [subject to] me'ilah, property of Jews, property that is owned, and anywhere except [on] the premises owned by the damager and the premises of the damagee and the damager. When he damages, the damager is obligated to pay for the damage with the best of the land.