Once the Prophet ﷺ ordered a person on 'Ashura' (the tenth of Muharram) to announce, "Whoever has eaten, should not eat any more, but fast, and who has not eaten should not eat, but complete his fast (till the end of the day).  

أَنَّ النَّبِيَّ ﷺ بَعَثَ رَجُلاً يُنَادِي فِي النَّاسِ يَوْمَ عَاشُورَاءَ أَنْ مَنْ أَكَلَ فَلْيُتِمَّ أَوْ فَلْيَصُمْ وَمَنْ لَمْ يَأْكُلْ فَلاَ يَأْكُلْ  

"The Prophet ﷺ sent a messenger to the village of the Ansar in the morning of the day of 'Ashura' (10th of Muharram) to announce: 'Whoever has eaten something should not eat but complete the fast, and whoever is observing the fast should complete it.' "She further said, "Since then we used to fast on that day regularly and also make our boys fast. We used to make toys of wool for the boys and if anyone of them cried for, he was given those toys till it was the time of the breaking of the fast."  

أَرْسَلَ النَّبِيُّ ﷺ غَدَاةَ عَاشُورَاءَ إِلَى قُرَى الأَنْصَارِ مَنْ أَصْبَحَ مُفْطِرًا فَلْيُتِمَّ بَقِيَّةَ يَوْمِهِ وَمَنْ أَصْبَحَ صَائِمًا فَلْيَصُمْ قَالَتْ فَكُنَّا نَصُومُهُ بَعْدُ وَنُصَوِّمُ صِبْيَانَنَا وَنَجْعَلُ لَهُمُ اللُّعْبَةَ مِنَ الْعِهْنِ فَإِذَا بَكَى أَحَدُهُمْ عَلَى الطَّعَامِ أَعْطَيْنَاهُ ذَاكَ حَتَّى يَكُونَ عِنْدَ الإِفْطَارِ