Once Hazrat Moulana Ashraf Ali Thanwi (rahmatullahi ‘alaihi) mentioned that a well-known proverb in the Arabic language is:
“Live like brothers but deal like strangers”
There are many advantages and benefits through one adopting clarity and system in one’s dealings, whether one takes a loan, gives a loan, or one settles an outstanding debt, in all cases one should ensure that one reduces it in writing and one keeps a record of the transaction. In this way one will save oneself from inconvenience or incurring any loss. For example, when one hires the services of the washer-man (laundromat) then he should ensure that he asks for a receipt as a proof of the transaction. In doing so, one benefit one receives is that in the event the clothes get misplaced by the washer-man (laundromat), the washer-man will not be able to deny that you gave your clothes to him, as you have proof of the transaction. Another benefit one receives is that even if one loses the receipt, since one had taken a receipt from the washer-man, the washer-man will remain constantly aware and conscious that he had given you a receipt for your clothes, hence he will certainly return your clothes to you. These beautiful teachings of sharee’ah (i.e. recording the transaction, business dealings, etc.) that we have received are all favours and bounties upon us from Allah Ta’ala.
(Malfoozaat Hakeemul Ummat 10/ 62)