Yahya related to me from Malik that he had heard that Abdullah ibn Umar used to be asked, "Can some one fast for some one else, or do the prayer for some one else?" and he would reply, "No one can fast or do the prayer for anyone else."
أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ يُسْأَلُ هَلْ يَصُومُ أَحَدٌ عَنْ أَحَدٍ أَوْ يُصَلِّي أَحَدٌ عَنْ أَحَدٍ فَيَقُولُ لَا يَصُومُ أَحَدٌ عَنْ أَحَدٍ وَلَا يُصَلِّي أَحَدٌ عَنْ أَحَدٍ