唐僧师(shī )(🍅)徒四(👷)人前去西天取经,途经荒山野(yě )岭,巧遇一(🕸)位破衣烂衫和尚(shàng ),要他们(men )师(shī )徒捎带一(🍖)些羊(🏴)皮背囊交与如来佛祖。此背囊(❣)所装之物(wù )(📼),谓(🚤)“有即是无(🔸),无(🎩)即是(🗄)有(🛍)",只要你心(💆)中想要什么,就(🚥)会有什么,实为一件非常神奇的(🚸)法宝。但和尚(shàng )要唐(táng )(🐖)僧师徒下(⏺)以诚信保证,就是在(zài )(📯)把背(🛑)囊(náng )(⏯)交给如来(lái )(❔)佛祖之前,无论遇到什(shí )么(🙂),都不许打开,更不(bú )能盗用囊中之(zhī )物。唐(táng )僧师徒一(🥫)口(kǒu )应(yīng )承。临走前,和尚(💠)把(bǎ )用来打开(kāi )背囊的口诀分三句分别告(gào )诉孙(sūn )悟(wù )空(❕)、猪(zhū )八戒(jiè )和沙和尚。师(🚗)徒(tú )一行重又(➡)上(shàng )路(lù )。小牛王(wáng )(👪)得知此事,对(duì )(🌼)背囊垂涎欲滴,召集天神(shén )天将(🈺)后代(📧),执意占(zhàn )为已(yǐ )有。小牛(niú )(🥤)王(wáng )乃牛魔王(🥅)和(hé )铁扇公(🔞)主的娇养(yǎng )(🔎)独子……