The Samveda is derived almost entirely from the Rigveda, with much common text. So also our Constitution. About four-fifths of that voluminous document is taken from the Government of India Act of 1935, much of it word for word. But it is the new stuff that is actually in it, and also the material that was deliberately left out, that makes it a text that was good enough to have survived the decades in such good shape.
All around us, constitutions have failed (Pakistan is currently, if I am not mistaken, on its fourth edition), while ours has carried us

)