From Chapter 24 - Tai Chi - The Origin of Soft Subduing Hard:
Recognising the danger of the situation, Zhang Wuji used his sword to
block. With great skill, Fang Dongbai adjusted his stance slightly. The
Heaven Sword now attacked from the side. With a 'qing' sound, six inches
of the wooden sword was cut off. The minor obstruction was not enough to
hold back the Heaven Sword and it stabbed straight at Zhang Wuj's chest.
In shock, Zhang Wuji shot his left land out and caught the sword between
his index and middle fingers. At the same time, the broken wooden sword
in his right hand chooped down on Fang Dongbai's right arm. Though it
was a wooden sword, when backed with the power of the Art of 9 Yang it
was no different from a steel blade. Fang Dongbai tried to pull his
right arm back but Zhang Wuji's two fingers held onto the Heaven Sword
with an iron-grip. In this circumstances, his only option was to let go
of the Heaven Sword and jump away. Only to hear Zhang Wuji yell: ?Let
go!? Fang Dongbai gritted his teeth but held on to the sword. In a blink
of an eye a 'pa' sound was heard. His arm, still holding on to the
sword, was cut off by the wooden sword. Fang Dongbai refused to let go
of the sword because he wanted to protect it. He stretched out his left
hand and snatched the falling right arm out of the air. Though the arm
had left its body, its five fingers still held on firmly to the Heaven
Sword. Zhang Wuji was stunned at this display of courage. He also felt
regret. So he did not try to take the sword. Fang Dongbai walked in
front of Zhao Min, bowed and said: ?My lady, your servant is useless. I
should be punished.? Zhao Min completely ignored him. She said: ?Today
we'll give Sect Leader Zhang face and let Wudang Sect off.?