Mother Sister Prostitute

A good wife is one who

1. serves her husband in the morning like a mother does, 
2. loves him in the day like a sister does and 
3. pleases him like a prostitute in the night. 

Explanation :

1. Like Mother : Get him Ready For Day's Job 
2. Like Sister : Be a Friend to Support Him in Trials of Day 
3. Like Prostitute : Provide all Physical Requirements - to Ensure loyalty