What was narrated concerning the reward of one who (loses) his child Sunan Ibn Majah 1606

Arabic hadith text
حَدَّثَنَا نَصْرُ بْنُ عَلِيٍّ الْجَهْضَمِيُّ، حَدَّثَنَا إِسْحَاقُ بْنُ يُوسُفَ، عَنِ الْعَوَّامِ بْنِ حَوْشَبٍ، عَنْ أَبِي مُحَمَّدٍ، مَوْلَى عُمَرَ بْنِ الْخَطَّابِ عَنْ أَبِي عُبَيْدَةَ، عَنْ عَبْدِ اللَّهِ، قَالَ: قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ مَنْ قَدَّمَ ثَلاَثَةً مِنَ الْوَلَدِ لَمْ يَبْلُغُوا الْحِنْثَ كَانُوا لَهُ حِصْنًا حَصِينًا مِنَ النَّارِ ‏"‏ ‏.‏ فَقَالَ أَبُو ذَرٍّ: قَدَّمْتُ اثْنَيْنِ ‏.‏ قَالَ: ‏"‏ وَاثْنَيْنِ ‏"‏ ‏.‏ فَقَالَ أُبَىُّ بْنُ كَعْبٍ أَبُو الْمُنْذِرِ سَيِّدُ الْقُرَّاءِ: قَدَّمْتُ وَاحِدًا ‏.‏ قَالَ" ‏"‏ وَوَاحِدًا ‏"
Translation
It wasnarrated from ‘Abdullah that the Messenger of Allah (ﷺ)said

“Whoever sends fourth three of his children who had not reachedtheage of puberty, they will be a strong fortification for himagainstthe Fire.” Abu Dharr said: “I sent forth two.” He said: “Andtwo” Ubayy bin Ka’b, the chief of the reciters, said: “I sentforthone.” He said: “Even one.”