It was narrated to us by Moḥammed bin Ibrāhīm رحمه الله, who said – it was narrated to us by Aḥmed bin Moḥammed  al-Hamdāni, who said – it was reported to us by ʿAlī bin al-Ḥassan bin ʿAlī bin Fadhāl, from his father:1

From Abī al-Ḥassan ʿAlī bin Mūsa al-Ridha عليه السلام, whereupon he said: Indeed, in Khorasān there is a place that a time will come upon it where it will have angels come and go. There won’t be a moment where a group of them descends from the skies and a group of them ascend, until the trumpet is blown.
He was asked: Oh son of the Messenger of Allāh, which place is this?
He said: It is in the land of Ṭūs, and it is – by Allāh – from the gardens of Paradise. Whoever visits me in this place, it is as if he also visited the Messenger of Allāh صلى الله عليه وآله; and Allāh, Blessed and High, writes for him the reward of one thousand accepted Ḥajjs and one thousand accepted ʿumrahs; and He prescribes that my forefathers and I will be intercessors for him on the Day of Judgement.

1. This narration has a reliable chain. al-Shaykh Hādi al-Najafi says this ḥadīth has a reliable (mawathaq) chain [Mawsūʿat al-Aḥādīth ahl al-Bayt, Volume 4, Page 431].

حدثنا محمد بن إبراهيم ( رحمه الله ) ، قال : حدثنا أحمد بن محمد الهمداني ، قال : أخبرنا علي بن الحسن بن علي بن فضال ، عن أبيه ، عن أبي الحسن علي بن موسى الرضا ( عليه السلام ) أنه قال : إن بخراسان لبقعة يأتي عليها زمان تصير مختلف الملائكة ، فلا يزال فوج ينزل من السماء وفوج يصعد إلى أن ينفخ في الصور . فقيل له : يا بن رسول الله ، وأية بقعة هذه ؟ قال : هي بأرض طوس ، وهي والله روضة من رياض الجنة ، من زارني في تلك البقعة كان كمن زار رسول الله ( صلى الله عليه وآله ) ، وكتب الله تبارك وتعالى له بذلك ثواب ألف حجة مبرورة وألف عمرة مقبولة ، وكنت أنا وآبائي شفعاؤه يوم القيامة .