@Licilou
Really? I don't remember that part well in the donghua, but it's weird because the book makes it clear that it was an accident :
"Wei WuXian was inspecting the area of the cave as he backed away with the fires. Suddenly, pain burst through his arm. Looking down, he saw that he had been shot by an arrow. It turned out that the Lan Sect disciple that Lan WangJi had glared at picked up one of the bows the Wen Sect had left and shot at the beast. However, perhaps realizing how fearsomely agile it was, his hand had slipped and the arrow had lost its aim, landing on Wei WuXian instead. Wei WuXian had no time to pull it out, hitting the ground with his palm again. He only cursed after the flame had appeared, “Back off!! Don’t cause me any trouble!”
The disciple had originally wanted to hit the beast’s vital spot with just one shot, so that he could save some of the face that he had lost. However, he never expected it to turn out like this. Face paler than ever, he threw himself into the water and fled as fast as he could. Jiang Cheng hurried Wei WuXian, “Get over here!”"
(From Exiled Rebels' translation, chapter 53, part 3)