Hadith 31-229

وَبِهذَا الإسناد قالَ: قالَ النَّبِي‏ صَلَّى اللهُ عَلَيْهِ وَآلِهِ: يا عَلِيُّ أَنْتَ تَبرَاُ ذَمَّتي، وَأَنْتَ خَلِيفَتِي عَلَى اُمَّتي.

According to the same documentation, the Prophet (S) said, “O Ali! You will take over my responsibilities. You are my Representative over my nation after me.”