I stayed with Aḥmad b. Ḥanbal and he brought me water.  In the morning he found that I had not used it, so he said: “A scholar of Hadeeth does not offer prayers during the night?!”  I said, “I am a traveler.”  He replied, “Even though you are a traveler!  Masrooq performed Hajj and he did not sleep without prostrating.”

—’Abdus-Samad Sulaiman b. Mater

[Tabaqat al-Hanabilah, vol. 1, p. 217.  Also Al-Manaqib by Ibn al-Jawzi, p. 273]

(Read on pg 125, Salahuddin Ali Abdul Mawjood, The Biography of Imam Ahmad bin Hanbal. Darussalam. Riyadh: 2006.)