ENOfficial
Anas reported God’s Messenger as saying, “If anyone prays twelve rak'as in the forenoon God will build for him a castle of gold in paradise.” Tirmidhi and Ibn Majah transmitted it, but Tirmidhi said, “This is a gharib tradition which I know only by this line of transmission.”
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَنَسٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ صَلَّى الضُّحَى ثِنْتَيْ عَشْرَةَ رَكْعَةً بَنَى اللَّهُ لَهُ قَصْرًا مَنْ ذَهَبٍ فِي الْجَنَّةِ» . رَوَاهُ التِّرْمِذِيُّ وَابْنُ مَاجَهْ وَقَالَ التِّرْمِذِيُّ: هَذَا حَدِيثٌ غَرِيبٌ لَا نَعْرِفُهُ إِلَّا مِنْ هَذَا الْوَجْهِ
sunnah.com