Hello Abdul
Actually, the destination MAC address comes first, and there is a good reason for this. Switches will forward frames in one of two ways:
You can click on each of those to find out more details about them. Cut-through switching is the default on most modern switches. As the frame enters the switch, as soon as the destination MAC address is read, the frame is forwarded out of the appropriate exit interface without waiting to receive the whole frame.
By making the destination field appear first in the header, the frame can be forwarded sooner, and thus a higher throughput is achieved.
I hope this has been helpful!
Laz