This master turned out to be corrupt and was put into a well for punishment, where he became a three-legged toad. Liu Hai's attempts to save his master repeatedly failed. Finally, Liu Hai came up with the idea of tying a silk thread to a traditional Chinese coin, which he threw into the well. When his teacher saw the coin, he couldn't help but bite.
傳說仙人劉海曾拜一位守財奴為師學道，師父卻因貪污被罰關入井中，化為三足蟾蜍，劉海屢救不成，最後靈機一動，以長長的絲線綁上銅錢，見錢眼開的師父果真就上鉤了。