Sunan Abi Dawud 1972

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ الزُّهْرِيُّ، حَدَّثَنَا سُفْيَانُ، عَنْ مِسْعَرٍ، عَنْ وَبَرَةَ، قَالَ سَأَلْتُ ابْنَ عُمَرَ مَتَى أَرْمِي الْجِمَارَ قَالَ إِذَا رَمَى إِمَامُكَ فَارْمِ ‏.‏ فَأَعَدْتُ عَلَيْهِ الْمَسْأَلَةَ فَقَالَ كُنَّا نَتَحَيَّنُ زَوَالَ الشَّمْسِ فَإِذَا زَالَتِ الشَّمْسُ رَمَيْنَا ‏.‏

Narrated Wabrah:I asked Ibn 'Umar: When should I throw pebbles at the jamrah? He replied: When your imam (leader at Hajj) throws pebbles, at that time you should throw them. I repeated the question to him. Thereupon he said: We used to wait for the time when the sun passes the meridian. When the sun declined, we threw the pebbles