Abu Hurayrah radhiallahu `anhu has said that the Messenger of Allah sallallahu `alayhi wa sallam mentioned a man of the Bani Israel saying:
He asked another to lend him a thousand dinars. The lender asked him to bring witnesses but the borrower said, “Allah is sufficient as a witness.” The lender asked him to furnish a surety but the borrower again asserted, “Allah is sufficient as a surety.” The lender agreed, “You are correct,” and lent him money for a specified period.
The debtor went across the sea. When he had finished his work, he looked for a conveyance to take him back for the punctual repayment of his debt, but he did not find any conveyance. So he took a piece of wood and made a hole in it. He inserted in it the one thousand dinars and a letter to the lender and closed the hole tightly.
He took the piece of wood to the sea and said, “O Allah! You know well that I took a loan of one thousand dinars from so-and-so. He demanded a surety from me but I told him that Allah’s surety was enough and he accepted Your Guarantee. He then demanded a witness and I told him that Allah was sufficient as a witness. No doubt I have tried much to find a conveyance so that I might pay back his money but could not find one, so I hand this money over to you.”
Saying that, he threw the piece of wood into the sea till it went far out into it, and then he went away. Meanwhile he kept looking for a conveyance to take him to the lender’s place.
One day, the lender came out of his house to see whether a ship had arrived bringing his money, and all of a sudden, he saw a piece of wood in which was the money. He took it home to use as firewood. When he sawed it, he found his money and the letter inside it.
Shortly after that, the debtor came with a thousand dinars and said, “By Allah! I had been trying to get a boat so I could bring you your money but failed to get one before the one I have come by.”
The lender said, “Allah has delivered on your behalf the money you sent in the piece of wood. So you may keep your thousand dinars and go, guided on the right path.”
~ Sahih Bukhari