The Meaning of Mu'min, or Believer
`Ali bin Abi Talhah narrated from Ibn `Abbas, about,
[إِنَّ الَّذِينَ ءَامَنُواْ وَالَّذِينَ هَادُواْ وَالنَّصَـرَى وَالصَّـبِئِينَ مَنْ ءَامَنَ بِاللَّهِ وَالْيَوْمِ الاٌّخِرِ]
(Verily, those who believe and those who are Jews and Christians, and Sabians, whoever believes in Allah and the Last Day) that Allah revealed the following Ayah afterwards,
[وَمَن يَبْتَغِ غَيْرَ الإِسْلَـمِ دِينًا فَلَن يُقْبَلَ مِنْهُ وَهُوَ فِى الاٌّخِرَةِ مِنَ الْخَـسِرِينَ ]
(And whoever seeks religion other than Islam, it will never be accepted of him, and in the Hereafter he will be one of the losers) (3:85).
This statement by Ibn `Abbas indicates that Allah does not accept any deed or work from anyone, unless it conforms to the Law of Muhammad that is, after Allah sent Muhammad . Before that, every person who followed the guidance of his own Prophet was on the correct path, following the correct guidance and was saved.