《太平广记·卷二百四十九·诙谐五》
一次，在社坛里做祭祀前的洁身静心准备时，长孙玄同坐在帐幕里面，来了一条狗，往坛墙上撒尿。
于坛所清斋，玄同在幕内坐。有犬来，遗粪秽于墙上。
Once, while he was preparing for a sacrifice in the temple, Changsun Xuantong was sitting inside the tent, when a dog came and peed on the wall of the altar.