Take the painting with you
when you leave the taxi.
Leave the painting
on the back seat of the taxi "accidentally".
Just as you're closing the taxi door, the stranger tosses his package inside. You can see it's a painting, wrapped in brown paper. The driver sets off, informing you that he's taking you to the address he was given by despatch so if you're not who you say you are then tough luck.
En route, a quick peek at the painting reveals that it's of none other than insane Nazi dictator Adolf Hitler.
Presently, the driver arrives at your hotel.
You can:
Take the painting with you
when you leave the taxi.
Leave the painting
on the back seat of the taxi "accidentally".