Musnad Ahmad 442
it was narrated that Abu Salih, the freed slave of `Uthman, said:
I heard `Uthman in Mina saying:  O people, I shall tell you a hadeeth that I heard from the Messenger of Allah (ﷺ) . He said: `Standing guard on the border for one day for the sake of Allah is better than one thousand ordinary days, so let a man stand on guard at the border as much as he wants.” [`Uthman] said; Have I conveyed [the message]? They said: Yes. He said: O Allah, bear witness.
حَدَّثَنَا أَبُو سَعِيدٍ، مَوْلَى بَنِي هَاشِمٍ حَدَّثَنَا ابْنُ لَهِيعَةَ، حَدَّثَنَا زُهْرَةُ بْنُ مَعْبَدٍ، عَنْ أَبِي صَالِحٍ، مَوْلَى عُثْمَانَ أَنَّهُ حَدَّثَهُ قَالَ سَمِعْتُ عُثْمَانَ، بِمِنًى يَقُولُ يَا أَيُّهَا النَّاسُ إِنِّي أُحَدِّثُكُمْ حَدِيثًا سَمِعْتُهُ مِنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ رِبَاطُ يَوْمٍ فِي سَبِيلِ اللَّهِ أَفْضَلُ مِنْ أَلْفِ يَوْمٍ فِيمَا سِوَاهُ فَلْيُرَابِطْ امْرُؤٌ كَيْفَ شَاءَ هَلْ بَلَّغْتُ قَالُوا نَعَمْ قَالَ اللَّهُمَّ اشْهَدْ‏.‏