One of the base requirements for making it to Paradise in the Hereafter is that one needs to believe in the Hereafter.
[2:62] Surely, those who believe, those who are Jewish, the Christians, and the converts; anyone who (1) believes in GOD, and (2) believes in the Last Day, and (3) leads a righteous life, will receive their recompense from their Lord. They have nothing to fear, nor will they grieve.
إِنَّ الَّذِينَ آمَنُوا وَالَّذِينَ هَادُوا وَالنَّصَارَىٰ وَالصَّابِئِينَ مَنْ آمَنَ بِاللَّهِ وَالْيَوْمِ الْآخِرِ وَعَمِلَ صَالِحًا فَلَهُمْ أَجْرُهُمْ عِنْدَ رَبِّهِمْ وَلَا خَوْفٌ عَلَيْهِمْ وَلَا هُمْ يَحْزَنُونَ
But for a person to prove that they really believe something then their actions should correspond with their stated belief, otherwise the claim is nothing but lip service. For instance, if an investor claims that the market is going to crash then we would expect that his positions in the market would match this belief, but if we see that it doesn’t then it is a sign that he doesn’t really believe what he states. Similarly, God gives us three conditions for us to gauge if a person genuinely believes in the Hereafter or not.
- They are dissatisfied with the mention of God alone and only content when others are mentioned beside the God.
[39:45] When GOD ALONE is mentioned, the hearts of those who do not believe in the Hereafter shrink with aversion. But when others are mentioned beside Him, they become satisfied.
وَإِذَا ذُكِرَ اللَّهُ وَحْدَهُ اشْمَأَزَّتْ قُلُوبُ الَّذِينَ لَا يُؤْمِنُونَ بِالْآخِرَةِ وَإِذَا ذُكِرَ الَّذِينَ مِنْ دُونِهِ إِذَا هُمْ يَسْتَبْشِرُونَ
- They object to the Quran alone.
[17:45] When you read the Quran, we place between you and those who do not believe in the Hereafter an invisible barrier. [17:46] We place shields around their minds, to prevent them from understanding it, and deafness in their ears. And when you preach your Lord, using the Quran alone, they run away in aversion.
وَإِذَا قَرَأْتَ الْقُرْآنَ جَعَلْنَا بَيْنَكَ وَبَيْنَ الَّذِينَ لَا يُؤْمِنُونَ بِالْآخِرَةِ حِجَابًا مَسْتُورًا
وَجَعَلْنَا عَلَىٰ قُلُوبِهِمْ أَكِنَّةً أَنْ يَفْقَهُوهُ وَفِي آذَانِهِمْ وَقْرًا وَإِذَا ذَكَرْتَ رَبَّكَ فِي الْقُرْآنِ وَحْدَهُ وَلَّوْا عَلَىٰ أَدْبَارِهِمْ نُفُورًا
- They accept other source as religious law other than the word of God.
[6:112] We have permitted the enemies of every prophet—human and jinn devils—to inspire in each other fancy words, in order to deceive. Had your Lord willed, they would not have done it. You shall disregard them and their fabrications. [6:113] This is to let the minds of those who do not believe in the Hereafter listen to such fabrications, and accept them, and thus expose their real convictions.
وَكَذَٰلِكَ جَعَلْنَا لِكُلِّ نَبِيٍّ عَدُوًّا شَيَاطِينَ الْإِنْسِ وَالْجِنِّ يُوحِي بَعْضُهُمْ إِلَىٰ بَعْضٍ زُخْرُفَ الْقَوْلِ غُرُورًا وَلَوْ شَاءَ رَبُّكَ مَا فَعَلُوهُ فَذَرْهُمْ وَمَا يَفْتَرُونَ
وَلِتَصْغَىٰ إِلَيْهِ أَفْئِدَةُ الَّذِينَ لَا يُؤْمِنُونَ بِالْآخِرَةِ وَلِيَرْضَوْهُ وَلِيَقْتَرِفُوا مَا هُمْ مُقْتَرِفُونَ
This criteria can be used not only for others, but for ourselves as well. If we find that we are failing in one of these regards then perhaps it is an opportunity to reflect, repent, and reform before it is too late.