Hadithcore
Al-Adab Al-Mufrad, 154
sahih· Al-Albani

He said that the Messenger of Allah, (ﷺ), said, "Who do you reckon to be the childless among you?" They said, "They are those who do not have any children." No," he said, "The childless are those who have not sent any of their children ahead (i.e. none of their children have died)."

قَالَ‏:‏ وَقَالَ رَسُولُ اللهِ صلى الله عليه وسلم‏:‏ مَا تَعُدُّونَ فِيكُمُ الرَّقُوبَ‏؟‏ قَالُوا‏:‏ الرَّقُوبُ الَّذِي لاَ يُولَدُ لَهُ، قَالَ‏:‏ لاَ، وَلَكِنَّ الرَّقُوبَ الَّذِي لَمْ يُقَدِّمْ مِنْ وَلَدِهِ شَيْئًا‏.‏

References2 variants
In-Book Reference
Book 8, Hadith 12
English Reference
Book 8, Hadith 154