What happens if a person is only allowed four cubits of travel due to issues relating to the Shabbat limit on travel [Techum], but he needs to use the bathroom: Eruvin 41b
Learning modesty in use of the bathroom from cats: Eruvin 100b
The blessing recited after using the bathroom ["Asher Yatzar"]
Text of the blessing: Berachot 24b
Hygiene Issues and Dangers
Washing hands following using the bathroom: Berachot 15a
Proper method for wiping, using various sizes of stones: Shabbat 81a
Wiping with certain earths can cause bowel problems: Shabbat 81a
Wiping with a stone already used by someone else can cause bowel problems: Shabbat 81a
Non-Hygiene Dangers
Wiping one's self an even number of consecutive times: Pesachim 109b, 110a
Wiping one's self with pottery, can lead to danger from Magic: Shabbat 81b-82a
Wiping with an item which is flammable: Shabbat 82a
Using the bathroom after one of the dangerous Magic "Zugot"-Pairs: Pesachim 110a
Not using the bathroom, when one needs to: Shabbat 82a