ʿUyūn akhbār al-Riḍā
Hadith 228228 - وَبِإِسْنادِهِ قالَ: قالَ النَّبِي صَلَّى اللهُ عَلَيْهِوَآلِهِ: عَلِيٌّ أَوَّلُ مَنِ اتَّبَعَني وَهُوَأَوَّل مَن يُصافِحَهُ الحَقِّ.
31-228 According to the same documentation, the Prophet (S) said, “Ali (a.s.) was the first man who followed me. He is the first one whom God will encounter (in the Hereafter.”