Ibn 'Abbas said, " 'Umar said, 'Let us go forth to the land of our people.' Ubayy ibn Ka'b and I were at the back of the people. A cloud gathered. Ubayy said, 'O Allah, remove its harm from us!' We met the people and their mounts were wet. They said, 'What fell on us did not fall on you!' I said, 'He asked Allah Almighty to remove its harm from us.' 'Umar said, 'Why didn't you include us in your supplication?'"
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا ابْنُ أَبِي شَيْبَةَ، قَالَ: حَدَّثَنَا يَحْيَى بْنُ عِيسَى، عَنِ الأَعْمَشِ، عَنْ حَبِيبٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ قَالَ: قَالَ عُمَرُ رَضِيَ اللَّهُ عَنْهُ: اخْرُجُوا بِنَا إِلَى أَرْضِ قَوْمِنَا. فَخَرَجْنَا، فَكُنْتُ أَنَا وَأُبَيُّ بْنُ كَعْبٍ فِي مُؤَخَّرِ النَّاسِ، فَهَاجَتْ سَحَابَةٌ، فَقَالَ أُبَيُّ: اللَّهُمَّ اصْرِفْ عَنَّا أَذَاهَا. فَلَحِقْنَاهُمْ، وَقَدِ ابْتَلَّتْ رِحَالُهُمْ، فَقَالُوا: مَا أَصَابَكُمُ الَّذِي أَصَابَنَا؟ قُلْتُ: إِنَّهُ دَعَا اللَّهَ عَزَّ وَجَلَّ أَنْ يَصْرِفَ عَنَّا أَذَاهَا، فَقَالَ عُمَرُ: أَلاَ دَعَوْتُمْ لَنَا مَعَكُمْ.
sunnah.com