The Messenger of Allah said to Ali: "Glad tiding O Ali! Verily you and your companions and your Shia (followers) will be in Paradise."

Sunni references:

Fadha'il al-Sahaba, by Ahmad Ibn Hanbal, v2, p655
Hilyatul Awliyaa, by Abu Nu'aym, v4, p329
Tarikh, by al-Khateeb al-Baghdadi, v12, p289
al-Awsat, by al-Tabarani
Majma' al-Zawa'id, by al-Haythami, v10, pp 21-22
al-Darqunti, who said this tradition has been transmitted via numerous authorities.
al-Sawa'iq al-Muhriqah, by Ibn Hajar Haythami , Ch. 11, section 1, p247

This shows the term shia 2 which I believe in was originally a political/ partisan term