Question Summary
Please explain what is considered tahajjud and its rulings.
Answer
In the Name of Allah, the Most Merciful and Compassionate
Tahajjud or night vigil prayer is an emphasized sunna. It is achieved by any voluntary prayer performed in the final third of the night after having slept. [Ibn ‘Abidin, Radd al-Muhtar]
If one has not slept, it is considered night worship (qiyam al-lail), not tahajjud.
Night Worship
Any voluntary prayer which is performed after ‘Isha is considered night worship.
The Messenger of Allah (may Allah bless him and give him peace) said, “One should perform prayer at night; even if (performed) sitting; even if to the length of milking a sheep. And any prayer performed after ‘Isha is considered of the night.” [Tabarani]
The Final Third of the Night
Even though you cannot sleep due to your occupation and wake up to perform tahajjud, the final third of the night is a blessed time in which prayers are answered, and a great reward is given.
The Messenger of Allah (may Allah bless him and give him peace) said, “Our Lord, Blessed and Exalted is He, descends (i.e., His mercy and concern descends) to the lowest heaven when the final third of the night remains and says, “Who is there to call on Me so I may answer them? Who is there to ask of Me so I may give them? Who is there to seek My forgiveness so I may forgive them?” [Bukhari]
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani