خلاصة الاقوال في معرفة الرجال - Page 276-277, Author: Allamah al-Hilli.
http://www.uofislam.net/uofislam/view.php?type=c_book&id=1360
مالك الاشتر قدس الله روحه ورضي الله عنه، جليل القدر، عظيم المنزلة، كان اختصاصه بعلي (عليه السلام) اظهر من ان يخفى، وتأسف
(أمير المؤمنين (عليه السلام) بموته، وقال: لقد كان لي كما كنت لرسول الله (صلى الله عليه وآله.
Ali a.s said, when Maalik al-Ashtar died: "He was to me as I was to Rasul Allah s.a.w.w"
And Ali a.s was to Rasul Allah s.a.w.w as Harun a.s was to Musa a.s. Therefore the relation of Malik Ashtar r.a with Imam Ali a.s was of the same nature as Ali a.s had with Rasul Allah s.a.w.w.