Muhammed bin Abi Haatim (rahimahullah) mentions:

On one occasion, Imaam Bukhaari (rahimahullah) was invited to the orchard of one of his companions. Imaam Bukhaari (rahimahullah) accepted the invitation and proceeded to the orchard. Thereafter, while at the orchard, Imaam Bukhaari (rahimahullah) began to perform nafl salaah. After completing his nafl salaah, Imaam Bukhaari (rahimahullah) lifted the hem of his kurta and said to one of his companions, “See if there is anything inside my kurta.”