وَ بِهَذَا الْإِسْنَادِ عَنْ مَرْوَكِ بْنِ عُبَيْدٍ عَنْ مُحَمَّدِ بْنِ زَيْدٍ الطَّبَرِيِّ قَالَ: كُنْتُ قَائِماً عَلَى رَأْسِ الرِّضَا ع- بِخُرَاسَانَ وَ عِنْدَهُ عِدَّةٌ مِنْ بَنِي هَاشِمٍ وَ فِيهِمْ إِسْحَاقُ بْنُ مُوسَى بْنِ عِيسَى الْعَبَّاسِيُّ فَقَالَ يَا إِسْحَاقُ بَلَغَنِي أَنَّ النَّاسَ يَقُولُونَ إِنَّا نَزْعُمُ أَنَّ النَّاسَ عَبِيدٌ لَنَا لَا وَ قَرَابَتِي مِنْ رَسُولِ اللَّهِ ص مَا قُلْتُهُ قَطُّ وَ لَا سَمِعْتُهُ مِنْ آبَائِي قَالَهُ وَ لَا بَلَغَنِي عَنْ أَحَدٍ مِنْ آبَائِي قَالَهُ وَ لَكِنِّي أَقُولُ النَّاسُ عَبِيدٌ لَنَا فِي الطَّاعَةِ مَوَالٍ لَنَا فِي الدِّينِ فَلْيُبَلِّغِ الشَّاهِدُ الْغَائِبَ

Narrated from Muhammad ibn Zayd al-Tabari who has said the following:

"I was in the presence of Imam al-Rida (عليه السلام) in Khurasan with a group of Hashimite people among them was Ishaq ibn Musa ibn Isa al-Abbasi."

The Imam (عليه السلام) said to Ishaq, “"I have come to know that people say that We claim that the people are Our slaves/servants (Abd). I swear upon my close relation with the Prophet of Allah (صلى الله عليه وآله), that I have never said such a thing, nor have I ever heard any such thing from My Father and Grandfather, nor I have received any such report from My ancestors who may have said any such thing. But I do say that people are Our slaves/servants (Abd) in the matters of obedience to Us. They are our followers in religion. So those present here must tell this to those who are not present here.

[Source: al-Kafi, Vol. 1, Pg. 187]