Chapter 1, Mishna 1, 2
How do we know that a yavam may acquire (marry) his yevama only through intercourse? How do we know that a yevama acquires herself (breaks the yibum obligation) only through chalitzah or the death of her yavam? How do we know that a wife may not leave her marriage via chalitzah? How is chalitzah performed? How do we know that a Hebrew slave may be acquired via money? WHat is the difference between a Hebrew slave who sold himself into slavery and one who was sold by the court because he stole and could not make restitution?