Sheikh `Abd al-Rahmân al-Barrâk
Commissioning someone who is going to Madinah to convey one's salutations to the Prophet (peace be upon him) is a baseless practice.
This behavior was never exhibited by the Companions, the Successors, the Pious Predecessors, or the people of knowledge.
There is no narration whatsoever to support it.
We know that the Prophet (peace be upon him) is informed about the salutations that his followers address to him.
The Prophet (peace be upon him) said: “Do not make my grave a festival place. Offer your salutations to me, for indeed your salutations will reach me from wherever you where” [Sunan Abî Dâwûd (2042)]
In another narration: “Your greeting will reach me from wherever you are.” [Musnad Abî Ya`lâ (469)]
Therefore, enlisting someone else to convey one's salutation to the Prophet (peace be upon him) is an unfounded innovation.
Indeed, commissioning others to convey one's salutations to the dead in general is unlawful. Though it is permissible to visit the dead at their graves and address one's greetings to them directly, it is not right to have someone else convey one's greetings to the grave on one's behalf.
The Prophet (peace be upon him) used to visit the graveyard of Baqî` and say salutations to the denizens of the graves, and he would supplicate for them. He taught his Companions to do the same, and he taught them what to say.
He said: say: "Peace be upon you, O inhabitants of this abode (i.e. “the graveyard”) from among the believers and Muslims. And, God willing, we shall be joining you. I beg of Allah peace for us and for you.” [Sahîh Muslim (975)]
Hence, salutation is being given directly from the live person to the dead. Allah has made matters easy for Muslims in that they can offer salutations on their Prophet (peace be upon him) from wherever they are, and they may do that as much as they like. They will be rewarded more for their increased salutations.
It is related that Allah has assigned some angels to inform the Prophet (peace be upon him) of these salutations on their behalf. [Musnad al-Bazzâr (1425, 1426) and al-Targhîb wa al-Tarhîb (1667-1664)]
And Allah knows best.
And may Allah's peace and blessing be upon our Prophet Muhammad.
Source: Islam Today