This is the special Du’aa related to the age of forty years old.
In Surah Al-Ahqaf (46): 15, Allah Ta’ala Says.”
وَوَصَّيۡنَا الۡاِنۡسَانَ بِوَالِدَيۡهِ اِحۡسَانًا ؕ حَمَلَـتۡهُ اُمُّهٗ كُرۡهًا وَّوَضَعَتۡهُ كُرۡهًا ؕ وَحَمۡلُهٗ وَفِصٰلُهٗ ثَلٰـثُوۡنَ شَهۡرًا ؕ حَتّٰٓى اِذَا بَلَغَ اَشُدَّهٗ وَبَلَغَ اَرۡبَعِيۡنَ سَنَةً ۙ قَالَ رَبِّ اَوۡزِعۡنِىۡۤ اَنۡ اَشۡكُرَ نِعۡمَتَكَ الَّتِىۡۤ اَنۡعَمۡتَ عَلَىَّ وَعَلٰى وَالِدَىَّ وَاَنۡ اَعۡمَلَ صَالِحًا تَرۡضٰٮهُ وَاَصۡلِحۡ لِىۡ فِىۡ ذُرِّيَّتِىۡ ؕۚ اِنِّىۡ تُبۡتُ اِلَيۡكَ وَاِنِّىۡ مِنَ الۡمُسۡلِمِيۡنَ
{And We have enjoined upon man, to his parents, good treatment. His mother carried him with hardship and gave birth to him with hardship, and his gestation and weaning [period] is thirty months. [He grows] until, when he reaches maturity and reaches [the age of] forty years, he says, “My Lord, enable me to be grateful for Your favor which You have bestowed upon me and upon my parents and to work righteousness of which You will approve and make righteous for me my offspring. Indeed, I have repented to You, and indeed I am of the Muslims”} (15)