Asim bin Damra reported,
We asked Ali 
about the voluntary prayers of the Prophet ﷺ during the daytime.Ali said, "Those are sixteen rakats which the Messenger of Allah ﷺ used to pray voluntarily during the day, but few people maintain them regularly."Waki narrated to us, saying, my father said, Habib bin Abu Thabit said, "Abu Ishaq, I would not wish to exchange this hadith of yours for this mosque of yours filled with gold."
Ahmad 1208
Sahihحدثنا عبد الله حدثنا إسحاق بن إسماعيل وأبو خيثمة قالا حدثنا وكيع عن سفيان عن أبي إسحاق ح قال عبد الله و حدثني أبي حدثنا وكيع حدثنا سفيان وإسرائيل عن أبي إسحاق
عن عاصم بن ضمرة قال
سألنا عليا رضي الله عنه عن تطوع النبي ﷺ بالنهار قال قال علي تلك ست عشرة ركعة تطوع رسول الله ﷺ بالنهار وقل من يداوم عليها حدثنا وكيع قال وقال أبي قال حبيب بن أبي ثابت يا أبا إسحاق ما أحب أن لي بحديثك هذا ملء مسجدك هذا ذهبا
Its chains of transmission are sahih. Abdullah bin Ahmad narrated it from Ishaq bin Ismail Talaqani and Abu Khaythama and his father Imam Ahmad, all of them from Waki. This hadith is a repetition of 1202, and it has also preceded in longer form as 605, narrated by Imam Ahmad from Waki from Sufyan and Israil and his father, that is, Jarra bin Mulayh, the father of Waki. Following it also preceded the statement of Habib bin Abu Thabit which Waki narrated from his father, magnifying the importance of this hadith, and we noted there the error of Ibn Hajar and his assumption that this statement was praise of Harith Awar, a slip of attention on his part, since he thought it followed the hadith of Harith that comes after it, numbered 251. This is what confirms what we said, since there is no mention of Harith in this place, neither before it nor after it.