Is it permissible to visit the tomb of one of Allah's saints and supplicate there by saying: "O Allah, cure me by the blessing of my master Abdul Qadir"?

It is not permissible to intentionally visit graves to supplicate to Allah there, as this is an innovated bid'ah (religious innovation) that the Prophet (peace be upon him) did not command nor did the noble Companions practice. Furthermore, seeking intercession with Allah through the prestige of so-and-so, or their blessings, or their right, is a bid'ah and a means to shirk (polytheism), because it was not reported from the Prophet (peace be upon him) nor from the Companions.