Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said: "Through a single Hajj, Allah will admit a group of three people into Paradise: (1) the deceased, (2) the one who performs Hajj on his behalf, and (3) the one who carries it out (the executor)."
Abu Ma'shar here is Najih al-Sindi, a Madinan, and he is da'if (weak).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9855