Sparring isn't working at all. Should give monk 5% parry when getting hit by melee from front, then another 5% when monk hits target and another 5% when he gets hit again and so on (max 3 stacks).
Can't find it on wowhead anymore.
Spell ID: 116023 (probably, taken from some other wow database)
Spell definition:
"When you are attacked by a melee enemy in front of you, you begin to spar their attacks, increasing your chance to parry by 5% for 10 seconds. This effect has a 30 seconds cooldown.
When you attack them back, Sparring is amplified by an additional 5%. Stacks up to 3 times."
Proof:
https://i.imgur.com/rI9qqtn.jpg
