Allah commands that the property of the orphans be surrendered to them in full when they reach the age of adolescence, and He forbids using or confiscating any part of it. So He said;

﴿وَلاَ تَتَبَدَّلُواْ الْخَبِيثَ بِالطَّيِّبِ﴾

(and do not exchange (your) bad things for (their) good ones;) Sa`id bin Al-Musayyib and Az-Zuhri commented, "Do not substitute a weak animal of yours for a fat animal (of the orphans).'' Ibrahim An-Nakha`i and Ad-Dahhak commented, "Do not give something of bad quality for something of good quality.'' As-Suddi said, "One of them (caretakers of orphans) would take a fat sheep from the orphan's property and put in its place, a weak sheep of his, saying, `A sheep for a sheep.' He would also take a good Dirham and exchange it for a fake Dirham, saying, `A Dirham for a Dirham.''' Allah's statement,

﴿وَلاَ تَأْكُلُواْ أَمْوَلَهُمْ إِلَى أَمْوَلِكُمْ﴾

(and devour not their substance to your substance.) means, do not mix them together so that you eat up both, as Mujahid, Sa`id bin Jubayr, Muqatil bin Hayyan, As-Suddi and Sufyan bin Hassin stated. Allah said,

﴿إِنَّهُ كَانَ حُوباً كَبِيراً﴾

(Surely, this is a great sin. ), a major and substantial sin, according to Ibn `Abbas. This was also reported from Mujahid, `Ikrimah, Sa`id bin Jubayr, Al-Hasan, Ibn Sirin, Qatadah, Muqatil bin Hayyan, Ad-Dahhak, Abu Malik, Zayd bin Aslam and Abu Sinan. The meaning above is: adding their property to your property is a grave sin and a major mistake, so avoid it.