Now, for proclaiming 'emergency' who must provide written advice to the President?

The Union Cabinet

Answer: The Union Cabinet
The advice to the President to proclaim an Emergency must be given in writing by the Union Cabinet.

The Emergency at once brought out both the weaknesses and the strengths of India’s democracy. it brought out some ambiguities regarding the Emergency provision in the Constitution that have been rectified since. Now, an ‘internal’ Emergency can be proclaimed only on the grounds of ‘armed rebellion’ and it is necessary that the advice to the President to proclaim Emergency must be given in writing by the Union Cabinet.