ENOfficial
‘Abdallah b. ‘Amr reported God’s messenger as saying, “The supplication which gets the quickest answer is that made by one distant friend for another.” Tirmidhi and Abu Dawud transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسلم: «إِن أَسْرَعَ الدُّعَاءِ إِجَابَةً دَعْوَةُ غَائِبٍ لِغَائِبٍ» . رَوَاهُ التِّرْمِذِيّ وَأَبُو دَاوُد
sunnah.com