Narrated Abu Huraira (radiallaahu `anhu):
The Prophet (sallallaahu `alayhi wasallam) said, “A man from Bani Israel asked someone from Bani Israel to give him a loan of one thousand Dinars and the latter gave it to him. The debtor went on a voyage (when the time for the payment of the debt became due) but he did not find a boat, so he took a piece of wood and bored it and put 1000 dinars in it and threw it into the sea. The creditor went out and took the piece of wood to his family to be used as fire-wood.” And the Prophet (sallallaahu `alayhi wasallam) narrated the narration (and said), “When he sawed the wood, he found his money.”
Isn’t is amazing? The person who owed the other money had full intention to return it, but couldn’t find the means to. So he made a way for it, and Allah helped him with it. That pieced of wood could’ve been found by anyone, right? Allah’s plan. SubhanAllah.
Also, one must be sincere in his words and abide by his promises. Only then Allah will help him fulfill them, even if it takes a miracle.. or something like it. :)