Regarding filing of income tax return

if  the client receive any notice then respond I think you need not file any ITR as it is a gift received for the marriage  more respnsibility is on the person giving the gift

Gift received on the occassion of Marriage of the Assessee is not taxable.

But here the amount is received on Marriage of his son.

The amount is neither received from Relatives but from his friends.

So my view is that the amount would be taxable and it is to be shown under Other Sources.

Mr Karthik thanks for the reply 

Any Sum of Money received from A relative is exempt from Income Tax.

Since Son-in-law is covered under the definition of relative, it wont be taxable. There is no limits on the amount that can be transferred.