Q: Sister Aum Al-Bara’ from Abha, asks: What is the ruling on asking a person to supplicate Allah for them? One may ask another person to supplicate Allah for their sake during their travel or may ask them not to forget them during their supplications. Is it a kind of supplication to anyone other than Allah? Guide us to the right behavior in this regard. May Allah reward you with best.
A: It is permissible to ask a fellow Muslim brother or sister to supplicate Allah for one’s sake. It is not a kind of abhorred Tawassul (seeking to draw close to Allah through lawful means). Once, the Prophet (peace be upon him) said to his Companions: “A Yemeni person called Uuays Al-Qarni will come to you. He was dutiful to his mother. Whoever meets him from among you should ask him to ask Allah’s forgiveness for his sake.” It was reported also that he (peace be upon him) said to `Umar when he set on a journey to perform `Umrah (lesser pilgrimage): “Do not forget us in your supplication!”
There is no blame if one asks their brother to supplicate to Allah for their sake during their travel or to invoke Allah to grant them a righteous offspring or a wife. There is also no blame if one’s sister or mother asks them to supplicate Allah for her sake. It is permissible for a Muslim to ask his brother or sister to supplicate Allah for his sake.
Source : alifta.net : Browse by Volume Number > Volume 2 > Chapter on Tawassul