Authentic
graded by Salim al-Hilali
Companion’s words (mawquf) Muwatta Malik 674b
وَحَدَّثَنِي عَنْ مَالِك أَنَّهُ بَلَغَهُ 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
Yahya related to me from Malik that he had heard that Abdullah ibn Umar used to be asked, "an 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."
Reported by Malik (No. 674b, 676).