From Sahih Bukhari (Hadith 6261):
Narrated Abu Hurairah (ra):Allah's Messenger (ﷺ) mentioned a person from Bani Israel who took a piece of wood, made a hole in it, and put therein one thousand Dinar and letter from him to his friend. The Prophet (ﷺ) said, "(That man) cut a piece of wood and put the money inside it and wrote a letter from such and such a person to such and such a person
Reference: Bukhari 6261