It is reported on the authority of Abu Huraira:

We were sitting around the Messenger of Allah (ﷺ). Abu Bakr and Umar were also there among the audience. In the meanwhile the Messenger of Allah got up and left us, He delayed in coming back to us, which caused anxiety that he might be attacked by some enemy when we were not with him; so being alarmed we got up. I was the first to be alarmed. I, therefore, went out to look for the Messenger of Allah (ﷺ) and came to a garden belonging to the Banu an-Najjar, a section of the Ansar went round it looking for a gate but failed to find one. Seeing a rabi' (i. e. streamlet) flowing into the garden from a well outside, drew myself together, like a fox, and slinked into (the place) where God's Messenger was. He (the Prophet) said: Is it Abu Huraira? I (Abu Huraira) replied: Yes, Messenger of Allah. He (the Prophet) said: What is the matter with you? replied: You were amongst us but got up and went away and delayed for a time, so fearing that you might be attacked by some enemy when we were not with you, we became alarmed. I was the first to be alarmed. So when I came to this garden, I drew myself together as a fox does, and these people are following me. He addressed me as Abu Huraira and gave me his sandals and said: Take away these sandals of mine, and when you meet anyone outside this garden who testifies that there is no god but Allah, being assured of it in his heart, gladden him by announcing that he shall go to Paradise. Now the first one I met was Umar. He asked: What are these sandals, Abu Huraira? I replied: These are the sandals of the Messenger of Allah with which he has sent me to gladden anyone I meet who testifies that there is no god but Allah, being assured of it in his heart, with the announcement that he would go to Paradise. Thereupon 'Umar struck me on the breast and I fell on my back. He then said: Go back, Abu Huraira, So I returned to the Messenger of Allah (ﷺ), and was about to break into tears. 'Umar followed me closely and there he was behind me. The Messenger of Allah (may peace and blessings be on him) said: What is the matter with you, Abu Huraira? I said: I happened to meet 'Umar and conveyed to him the message with which you sent me. He struck me on my breast which made me fall down upon my back and ordered me to go back. Upon this the Messenger of Allah (ﷺ) said: What prompted you to do this, 'Umar? He said: Messenger of Allah, my mother and father be sacrificed to you, did you send Abu Huraira with your sandals to gladden anyone he met and who testified that there is no god but Allah, and being assured of it in his heart, with the tidings that he would go to Paradise? He said: Yes. Umar said: Please do it not, for I am afraid that people will trust in it alone; let them go on doing (good) deeds. The Messenger of Allah (ﷺ) said: Well, let them.

حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عُمَرُ بْنُ يُونُسَ الْحَنَفِيُّ، حَدَّثَنَا عِكْرِمَةُ بْنُ عَمَّارٍ، قَالَ حَدَّثَنِي أَبُو كَثِيرٍ، قَالَ حَدَّثَنِي أَبُو هُرَيْرَةَ، قَالَ كُنَّا قُعُودًا حَوْلَ رَسُولِ اللَّهِ صلى الله عليه وسلم مَعَنَا أَبُو بَكْرٍ وَعُمَرُ فِي نَفَرٍ فَقَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم مِنْ بَيْنِ أَظْهُرِنَا فَأَبْطَأَ عَلَيْنَا وَخَشِينَا أَنْ يُقْتَطَعَ دُونَنَا وَفَزِعْنَا فَقُمْنَا فَكُنْتُ أَوَّلَ مَنْ فَزِعَ فَخَرَجْتُ أَبْتَغِي رَسُولَ اللَّهِ صلى الله عليه وسلم حَتَّى أَتَيْتُ حَائِطًا لِلأَنْصَارِ لِبَنِي النَّجَّارِ فَدُرْتُ بِهِ هَلْ أَجِدُ لَهُ بَابًا فَلَمْ أَجِدْ فَإِذَا رَبِيعٌ يَدْخُلُ فِي جَوْفِ حَائِطٍ مِنْ بِئْرٍ خَارِجَةٍ - وَالرَّبِيعُ الْجَدْوَلُ - فَاحْتَفَزْتُ كَمَا يَحْتَفِزُ الثَّعْلَبُ فَدَخَلْتُ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏"‏ أَبُو هُرَيْرَةَ ‏"‏ ‏.‏ فَقُلْتُ نَعَمْ يَا رَسُولَ اللَّهِ ‏.‏ قَالَ ‏"‏ مَا شَأْنُكَ ‏"‏ ‏.‏ قُلْتُ كُنْتَ بَيْنَ أَظْهُرِنَا فَقُمْتَ فَأَبْطَأْتَ عَلَيْنَا فَخَشِينَا أَنْ تُقْتَطَعَ دُونَنَا فَفَزِعْنَا فَكُنْتُ أَوَّلَ مَنْ فَزِعَ فَأَتَيْتُ هَذَا الْحَائِطَ فَاحْتَفَزْتُ كَمَا يَحْتَفِزُ الثَّعْلَبُ وَهَؤُلاَءِ النَّاسُ وَرَائِي فَقَالَ ‏"‏ يَا أَبَا هُرَيْرَةَ ‏"‏ ‏.‏ وَأَعْطَانِي نَعْلَيْهِ قَالَ ‏"‏ اذْهَبْ بِنَعْلَىَّ هَاتَيْنِ فَمَنْ لَقِيتَ مِنْ وَرَاءِ هَذَا الْحَائِطِ يَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ مُسْتَيْقِنًا بِهَا قَلْبُهُ فَبَشِّرْهُ بِالْجَنَّةِ ‏"‏ فَكَانَ أَوَّلَ مَنْ لَقِيتُ عُمَرُ فَقَالَ مَا هَاتَانِ النَّعْلاَنِ يَا أَبَا هُرَيْرَةَ ‏.‏ فَقُلْتُ هَاتَانِ نَعْلاَ رَسُولِ اللَّهِ صلى الله عليه وسلم بَعَثَنِي بِهِمَا مَنْ لَقِيتُ يَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ مُسْتَيْقِنًا بِهَا قَلْبُهُ بَشَّرْتُهُ بِالْجَنَّةِ ‏.‏ فَضَرَبَ عُمَرُ بِيَدِهِ بَيْنَ ثَدْيَىَّ فَخَرَرْتُ لاِسْتِي فَقَالَ ارْجِعْ يَا أَبَا هُرَيْرَةَ فَرَجَعْتُ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَأَجْهَشْتُ بُكَاءً وَرَكِبَنِي عُمَرُ فَإِذَا هُوَ عَلَى أَثَرِي فَقَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ مَا لَكَ يَا أَبَا هُرَيْرَةَ ‏"‏ ‏.‏ قُلْتُ لَقِيتُ عُمَرَ فَأَخْبَرْتُهُ بِالَّذِي بَعَثْتَنِي بِهِ فَضَرَبَ بَيْنَ ثَدْيَىَّ ضَرْبَةً خَرَرْتُ لاِسْتِي قَالَ ارْجِعْ ‏.‏ فَقَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ يَا عُمَرُ مَا حَمَلَكَ عَلَى مَا فَعَلْتَ ‏"‏ ‏.‏ قَالَ يَا رَسُولَ اللَّهِ بِأَبِي أَنْتَ وَأُمِّي أَبَعَثْتَ أَبَا هُرَيْرَةَ بِنَعْلَيْكَ مَنْ لَقِيَ يَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ مُسْتَيْقِنًا بِهَا قَلْبُهُ بَشَّرَهُ بِالْجَنَّةِ ‏.‏ قَالَ ‏"‏ نَعَمْ ‏"‏ ‏.‏ قَالَ فَلاَ تَفْعَلْ فَإِنِّي أَخْشَى أَنْ يَتَّكِلَ النَّاسُ عَلَيْهَا فَخَلِّهِمْ يَعْمَلُونَ ‏.‏ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ فَخَلِّهِمْ ‏"‏ ‏.‏