The Quran

وَأَمَّا الجِدارُ فَكانَ لِغُلامَينِ يَتيمَينِ فِي المَدينَةِ وَكانَ تَحتَهُ كَنزٌ لَهُما وَكانَ أَبوهُما صالِحًا فَأَرادَ رَبُّكَ أَن يَبلُغا أَشُدَّهُما وَيَستَخرِجا كَنزَهُما رَحمَةً مِن رَبِّكَ ۚ وَما فَعَلتُهُ عَن أَمري ۚ ذٰلِكَ تَأويلُ ما لَم تَسطِع عَلَيهِ صَبرًا

Muhammad Asad

"And as for that wall, it belonged to two orphan boys [living] in the town, and beneath it was [buried] a treasure belonging to them [by right].¹ Now their father had been a righteous man, and so thy Sustainer willed it that when they come of age they should bring forth their treasure by thy Sustainer's grace. "And I did not do [any of] this of my own accord:² this is the real meaning of all [those events] that thou wert unable to bear with patience."

I.e., left to them as an inheritance. Presumably that treasure would have been exposed to view if the wall had been allowed to tumble down, and would have been stolen by the avaricious village folk, who had shown their true character by refusing all hospitality to weary travellers.
Implying that whatever he had done was done under the impulsion of a higher truth - the mystic insight which revealed to him the reality behind the outward appearance of things and made him a conscious particle in God's unfathomable plan: and this explains the use of the plural "we" in verses 80-81, as well as the direct attribution, in the first paragraph of verse 82, of a concrete human action to God's will (Razi).