During an in-chamber hearing, district judge I S Mehta directed Malik to give his handwriting sample before Additional Chief Metropolitan Magistrate Gautam Manan, court sources said.
The NIA had sought the sample saying it has recovered some documents from the possession of co-accused Shakir Hussain Sheikh alias Chota Hafiz, who was killed in an encounter with security forces on December 20 last year in Kishtwar in Jammu and Kashmir, they said.
According to NIA, Sheikh, who was named as accused in the charge sheet and was absconding, was killed in an encounter and the judge abated proceedings against him.
Meanwhile, the court listed for hearing on March 12 the matter related to framing of additional charge of waging war against India against Malik for his alleged role in the September 7, 2011 terror attack at the court's reception in which 15 people were killed and 79 injured.
The trial judge had earlier declined the NIA's plea to prosecute Malik under the stringent charge which entails maximum punishment of death penalty, but the high court had ruled otherwise.