Menachot 44: Tzitzit Preventing One from Sin

On fulfilling the mitzvah of tzitzit, the Gemara tells us a story:

• a man was very stringent about tzitzit
• he sent 400 gold dinars to a prostitute living in a sea-side town to hire her
• the day of his appointment her maid let him enter
• She prepared six silver and one gold bed, with silver ladders and then a gold ladder between them
• She lay naked on the top bed and he went up to her but was hit in the face by his tzitzit
• he fell to the ground and she fell as well
• She swore, "By the Roman Capitol I will not leave you alone until you tell me what defect you saw in me"
• He replied "Never have I seen a woman as beautiful as you, but G-d commanded us tzitzit, and 'I am the Lord your G-d" is written twice to tell us that G-d will punish us in the future and G-d will reward us in the future.  The tzitzit were like witnesses testifying against me"
• She said "I will not leave you until you tell me your name, your town, your teacher, and your school". 
• He wrote this for her
• She divided her estate: 1/3 for the government, 1/3 for the poor, and 1/3 she took with her along with the beds
• at the Bet Madras of Rabbi Chiyya, she said "Master, teach your students about me and have them convert me"
• Rabbi Chiyya asked, "My daughter, perhaps you have set your eyes on one of the disciples?" 
• She showed him the handwritten note and he said, "Go and take possession of your purchase"
• The beds prepared for him in transgression could now be prepared for him halachically

The rabbis interpret this story in a number of ways.  Most agree that it teaches us about repentance based on love for G-d can turn sins into merits where we can reach greater states of holiness.