All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Seeking blessings entails asking for goodness and wealth from something. It is an act of worship, and acts of worship are not performed unless there are relevant Sharee‘ah proofs to support them. Thus, seeking blessings from graves is impermissible. This includes circumambulating them and rubbing oneself against the dust, walls and curtains of graves. The Prophet, sallallaahu ‘alayhi wa sallam, forbade Muslims from turning visits to his grave into grand occasions and feasts. [Ahmad and Abu Daawood]
In other words, the Prophet, sallallaahu ‘alayhi wa sallam, forbade Muslims from seeking blessings from his grave.
The Prophet, sallallaahu ‘alayhi wa sallam, also forbade Muslims from performing Salah (prayers) in front of or between graves. He did so to hold Muslims back from Shirk (polytheism), because they might seek blessings from graves and so turn from the permissible to the impermissible. Ibn Taymiyyah said that the Sharee‘ah forbids Muslims from striving to perform Salah (prayers) near graves, unlike the practices of Christians, and Muslims. This is understood from the words of Ibn Taymiyyah.
Allaah Knows best.