《太平广记·卷三百零三·神十三》
于是广琛想在墙上写首诗以表白心迹，可是笔硬是在墙上写不出字来。
于是琛乃题诗于其壁上，墨不成字。
Thus, Guangchen wanted to write a poem on the wall to express his heartfelt apology, but the brush was unable to write any words on the wall.