(Al-Baqara) 2 : 181
فَمَنْ بَدَّلَهُ بَعْدَمَا سَمِعَهُ فَإِنَّمَا إِثْمُهُ عَلَى الَّذِينَ يُبَدِّلُونَهُ ۚ إِنَّ اللَّهَ سَمِيعٌ عَلِيمٌ
Then anyone who alters it after hearing it, then indeed, the sin of it is upon those who alter it; Indeed, Lord Allah is the All-hearing, the All-knowing.
Whoever alters the bequest after hearing it, is a sinner. It is commanded in verse 5: 106 to do bequest in the presence of two believers. And if death approaches during a journey, in the absence of believers the bequest may be done in the presence of two honorable men.