Hadith 31-187

وَبِهذَا الإسناد قالَ: قالَ رَسُولَ اللَّهِ‏ صَلَّى اللهُ عَلَيْهِ وَآلِهِ: يا عَلِيِّ لَولاكَ لَما عُرِفَ الْمُؤْمِنُوُنَ بَعْدي.

According to the same documentation, God’s Prophet (S) said, “O Ali! Were it not for your existence, the believers after me would not get recognized.”