Since after demise of mother if he is legal heir of the property if there is no will in favour of third person. You can attach property through the order of court if the complete amount  is not recovered from.the said person. The details of the property can be given before.coirt with request of attachment.

Did mother die intestate or left any will 

2)  on her demise intestate husband , son and his siblings woukd be legal heirs of her property 

3) son share in property canbe attached 

If the borrower inherits his/her mother's property or becomes lawful owner of the property then on mentioning this court can attach the property for recovery of dues, if deem fit and necessary. This is normal rule of Civil procedures being followed by civil court. No case reference is required for this. Only mentioning the rule wiil be sufficient.

First you need transfer property from his mother's name to on his name and than attached flat to the loan or you can ask bank to confiscate this flat against loan.

If he is inheriting the property or part of the property to that extent only.

Borrower share can be attached through court order only. 

If he is the legal heir of the property then it can be attached to the effect of his share and loan amount

Dear Sir,

If that person is the legal heir of mother  and get that property for himself or a part of it as his share then you can file a suit and immediate attachment of the property under Order 38 Rule 5 of CPC.

Without commencement of trial and passing the judgement. How come court will order attachment. First get the ex pate order than file execution , than court will order attachment.

the defaulter is a legal heir of his mother

so he has an undivided share in the mother's flat

so that much share which the defaulter has in his mother's flat can be touched or taken as security by the lender towards security

if there are other legal heirs of mother, they would be having their respective undivided shares in the flat

so even if this flat is attached and is put up for sale, there will not be many buyers as no one likes to buy an undivided share of the house since the buyer would not get the possession 

but this share of the defaulter in his mother's flat can obviously be attached and be taken as security by the lender 

1. If he has inherited the property of his mother then the decree of the court for recovery of money can be executed against the property, meaning thereby that property can be attached in satisfaction of the decree, but for that there has to be a decree.

2. You file a suit for recovery of money and seek temporary injunction against the borrower to stop him from creating third party rights on the property during the pendency of the suit.

3. No reference case is required. Do not seek judgments on just anything.

This property is not in his name, hence you cannot seek to attach this property before judgment.

You can wait for him to change the property to his name  and then you may  file a recovery suit in which you can  ask for attachment  before judgment.

You can find out  from indiankaanoon.org where there are plenty  of case laws.