The great mujadid and hadith scholar, adherent of the shafi school of fiqh and Ashari school of theology, the teacher of Imam al-Bayhaqi (d.458H), Imam Abu Abdallah al-Hakim al-Nishapuri (321-403H), narrates in his book “Tariqh Naysaburi”,
in his biographical entry on Yahya bin Sabih, that dua at the latter’s grave his answered, in other words, it is a place of tawassul where dua is answered.
Similarly, Ibn Hajr al-Asqalani in his Tahdhib al-Tahdhib relates via Imam al-Hakim al-Nishapuri that:
Imam al-Hakim heard Imam Abu Ali al-Naysaburi saying, when he had extreme distress he saw the Prophet (peace be upon him) in his dream who said to go to the grave of Yahya bin Yahya (who is among the teachers of Imam Muslim) and to seek forgiveness and ask for his needs, and that he did so and his needs were obtained.
Imam Ibn al-Jawzi in his book al-Munthazam also narrates that,
Imam al-Hakim said that he heard Abu al-Hassan al-Siraj say that he saw in a dream the Prophet (peace & blessings be upon him) stop at the grave of Yahya bin Yahya, prayed and turned around and said “this tomb is a sanctuary (place of safety/security/refuge) for the people of this city”.