Sayyiduna al-Hajjaj bin Amr al-Mazini (may Allah be pleased with him) said: "Does any of you think that when he gets up at night and keeps praying until morning, he has prayed tahajjud? Tahajjud is only prayer after sleep, then prayer after sleep, then prayer after sleep. That is how the prayer of the Messenger of Allah (peace and blessings be upon him) used to be."
Imam al-Tabarani (may Allah have mercy on him) said: "These two hadiths are narrated from Sayyiduna al-Hajjaj bin Amr (may Allah be pleased with him) only with this chain; Ja'far bin Rabi'ah (may Allah have mercy on him) is alone in narrating them both."
Hadith Referenceالمعجم الأوسط / باب الميم / 8670
Hadith Gradingمحدثین:إسناده ضعيف، مداره على عبد الله بن صالح كاتب الليث
Hadith Takhrij«قال الهيثمي: مداره على عبد الله بن صالح كاتب الليث قال فيه عبد الملك بن شعيب ابن الليث ثقة مأمون وضعفه أحمد وغيره «مجمع الزوائد ومنبع الفوائد، ج 2، ص 277»» «أخرجه الطبراني فى «الكبير» برقم: 3216»