It is narrated from Sayyiduna Abdullah bin Ja'far (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Ali is my root and Ja'far is my branch, or Ja'far is my root and Ali is my branch."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13786