The horse has been a popular symbol in Hussain’s art. He saw a Duldul ( zuljana in Persian/ Urdu) as a child in a Muharram procession that his grandfather took him to.
The zuljana ( the pronunciation I am comfortable with & have always used) was a white mare used by the Prophet and then used by Imam Husain in Karbala.
It is the riderless zuljana that brought news of Imam Husain’s martyrdom to the ladies of his family in the camp.
Many imambaras keep a white horse to be used in the 10th Muharram@processions. No one rides it.
Apart from Muharram it is left to graze in a designated area.
This magnificent painting is at exhibition at @dag.world
