should i give to cashier his 5000 back?

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today i went to my bank to withdraw some cash with a friend of mine,i gave the cheque to my friend to withdraw it.when the bank cashier give him the cash he counted and gave me the cash, i just put the cash in my wallet without counting,that bank is a quite far away from my town,when i got hom and start counting the cash,finished counting and got surprised,bcuz there were Rs5000 more than the amount of my cheque. the confusin thing is that when i asked my friend about his counting, he said' cash is right. so now im confused. what should i do?