Is the Specification Of Intention Necessary For Voluntary Prayers (Nafl)? 

Question: What is the intention of nafl prayers?
In the Name of Allah, Most Merciful and Compassionate,
Assalamu ‘alaykum dear brother/ sister in faith,
The specification of the intention in prayer is required only for the five daily prayers (fard) and necessary prayer (wajib). It is not a requirement for voluntary prayers (nafl).  Your prayer is valid. [Shurunbulali, Nur al-Idah pg. 127]
Please see:
Allah, Most High, knows best.
[Ustadha] Iman Badawi
Checked and Approved by Shaykh Faraz Rabbani