Allah said,

﴿وَأَقِيمُواْ الصَّلَوةَ وَءَاتُواْ الزَّكَوةَ وَمَا تُقَدِّمُواْ لأَنْفُسِكُم مِّنْ خَيْرٍ تَجِدُوهُ عِندَ اللَّهِ﴾

(And perform the Salah and give the Zakah, and whatever of good you send forth for yourselves before you, you shall find it with Allah).

Allah encouraged the believers to busy themselves in performing deeds that would bring them benefit and reward on the Day of Resurrection, such as prayer and paying Zakah. This way, they will gain Allah's aid in this life and on a Day when the witnesses testify,

﴿يَوْمَ لاَ يَنفَعُ الظَّـلِمِينَ مَعْذِرَتُهُمْ وَلَهُمُ الْلَّعْنَةُ وَلَهُمْ سُوءُ الدَّارِ ﴾

(The Day when their excuses will be of no profit to the Zalimin (wrongdoers). Theirs will be the curse, and theirs will be the evil abode (i.e. painful torment in Hell-fire)) (40:52).

This is why Allah said,

﴿إِنَّ اللَّهَ بِمَا تَعْمَلُونَ بَصِيرٌ﴾

(Certainly, Allah sees what you do), meaning, that He is never unaware of the deeds of any person, nor will these deeds be lost by Him. Whether deeds are righteous or evil, Allah will award each according to what he or she deserves based on their deeds.

﴿وَقَالُواْ لَن يَدْخُلَ الْجَنَّةَ إِلاَّ مَن كَانَ هُودًا أَوْ نَصَـرَى تِلْكَ أَمَانِيُّهُمْ قُلْ هَاتُواْ بُرْهَـنَكُمْ إِن كُنتُمْ صَـدِقِينَ - بَلَى مَنْ أَسْلَمَ وَجْهَهُ لِلَّهِ وَهُوَ مُحْسِنٌ فَلَهُ أَجْرُهُ عِندَ رَبِّهِ وَلاَ خَوْفٌ عَلَيْهِمْ وَلاَ هُمْ يَحْزَنُونَ - وَقَالَتِ الْيَهُودُ لَيْسَتِ النَّصَـرَى عَلَى شَىْءٍ وَقَالَتِ النَّصَـرَى لَيْسَتِ الْيَهُودُ عَلَى شَىْءٍ وَهُمْ يَتْلُونَ الْكِتَـبَ كَذَلِكَ قَالَ الَّذِينَ لاَ يَعْلَمُونَ مِثْلَ قَوْلِهِمْ فَاللَّهُ يَحْكُمُ بَيْنَهُمْ يَوْمَ الْقِيَـمَةِ فِيمَا كَانُواْ فِيهِ يَخْتَلِفُونَ ﴾

(111. And they say, "None shall enter Paradise unless he be a Jew or a Christian.'' These are their own desires. Say (O Muhammad ), "Produce your Burhan if you are truthful.'') (112. Yes! But whoever submits his face (himself) to Allah (i.e. follows Allah's religion of Islamic Monotheism) and he is a Muhsin then his reward is with his Lord (Allah), on such shall be no fear, nor shall they grieve.) (113. The Jews said that the Christians follow nothing (i.e. are not on the right religion); and the Christians said that the Jews follow nothing (i.e. are not on the right religion); though they both recite the Scripture. Like unto their word, said those (the pagans) who know not. Allah will judge between them on the Day of Resurrection about that wherein they have been differing.)