It was narrated that ‘Ali bin Abi Talib said: “When Mughirah bin Shu’bah fought alongside the Prophet (ﷺ) he would carry a spear, and when he would come back he would throw his spear down so that someone would pick it up and give it back to him.” ‘Ali said to him: “I will tell the Messenger of Allah (ﷺ) about that.” He (the Prophet (ﷺ)) said: “Do not do that, for it you do that it will not be picked up as a lost item to be returned.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ إِسْمَاعِيلَ بْنِ سَمُرَةَ، أَنْبَأَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنْ أَبِي إِسْحَاقَ، عَنْ أَبِي الْخَلِيلِ، عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ، قَالَ كَانَ الْمُغِيرَةُ بْنُ شُعْبَةَ إِذَا غَزَا مَعَ النَّبِيِّ صلى الله عليه وسلم حَمَلَ مَعَهُ رُمْحًا فَإِذَا رَجَعَ طَرَحَ رُمْحَهُ حَتَّى يُحْمَلَ لَهُ . فَقَالَ لَهُ عَلِيٌّ لأَذْكُرَنَّ ذَلِكَ لِرَسُولِ اللَّهِ صلى الله عليه وسلم . فَقَالَ " لاَ تَفْعَلْ فَإِنَّكَ إِنْ فَعَلْتَ لَمْ تُرْفَعْ ضَالَّةٌ " .
sunnah.com