These Ayat sternly warn against those who hide the clear signs that the Messengers were sent with which guide to the correct path and beneficial guidance for the hearts, after Allah has made such aspects clear for His servants through the Books that He revealed to His Messengers. Abu Al-`Aliyah said that these Ayat, "were revealed about the People of the Scripture who hid the description of Muhammad ." Allah then states that everything curses such people for this evil act. Certainly, just as everything asks for forgiveness for the scholar, even the fish in the sea and the bird in the air, then those who hide knowledge are cursed by Allah and by the cursers. A Hadith in the Musnad, narrated through several chains of narrators, that strengthens the overall judgment of the Hadith, states that Abu Hurayrah narrated that Allah's Messenger ﷺ said:
«مَنْ سُئِلَ عَنْ عِلْمٍ فَكَتَمَهُ، أُلْجِمَ يَوْمَ الْقِيَامَةِ بِلِجَامٍ مِنْ نَار»
(Whoever was asked about knowledge that one has, but he hid it, then a bridle made of fire will be tied around his mouth on the Day of Resurrection.)
It is also recorded by Al-Bukhari that Abu Hurayrah said, "If it was not for an Ayah in Allah's Book, I would not have narrated a Hadith for anyone:
إِنَّ الَّذِينَ يَكْتُمُونَ مَآ أَنزَلْنَا مِنَ الْبَيِّنَـتِ وَالْهُدَى
(Verily, those who conceal the clear proofs, evidences and the guidance, which We have sent down,)"
Mujahid said, "When the earth is struck by drought, the animals say, `This is because of the sinners among the Children of Adam. May Allah curse the sinners among the Children of Adam."'
Abu Al-`Aliyah, Ar-Rabi` bin Anas and Qatadah said that
وَيَلْعَنُهُمُ اللَّـعِنُونَ
(and cursed by the cursers) means that the angels and the believers will curse them. Moreover, a Hadith states that everything, including the fish in the sea, asks for forgiveness for the scholars. The Ayah (2:159 above) states that those who hide the knowledge will be cursed, (in this life and) on the Day of Resurrection, by Allah, the angels, all humanity, and those who curse (including the animals) each in its own distinct way. Allah knows best.
From this punishment, Allah excluded all who repent to Him:
إِلاَّ الَّذِينَ تَابُواْ وَأَصْلَحُواْ وَبَيَّنُواْ
(Except those who repent and do righteous deeds, and openly declare (the truth which they concealed).)
This Ayah refers to those who regret what they have been doing and correct their behavior and, thus, explain to the people what they have been hiding.
فَأُوْلَـئِكَ أَتُوبُ عَلَيْهِمْ وَأَنَا التَّوَّابُ الرَّحِيمُ
(These, I will accept their repentance. And I am the One Who accepts repentance, the Most Merciful.)
This Ayah also indicates that those who used to call to innovation, or even disbelief, and repent to Allah, then Allah will forgive them. Allah afterwards states that those who disbelieve in Him and remain in this state until they die, then:
أُولَـئِكَ عَلَيْهِمْ لَعْنَةُ اللَّهِ وَالْمَلـئِكَةِ وَالنَّاسِ أَجْمَعِينَ
خَـلِدِينَ فِيهَآ
(it is they on whom is the curse of Allah and of the angels and of mankind, combined. They will abide therein (under the curse in Hell).)
Therefore, they will suffer the eternal curse until the Day of Resurrection and after that in the fire of Jahannam, where,
لاَ يُخَفَّفُ عَنْهُمُ الْعَذَابُ
(their punishment will neither be lightened)
Hence, the torment will not be decreased for them,
وَلاَ هُمْ يُنظَرُونَ
(nor will they be reprieved.)
The torment will not be changed or tempered for even an hour. Rather, it is continuous and eternal. We seek refuge with Allah from this evil end.
There is no disagreement that it is lawful to curse the disbelievers. `Umar bin Al-Khattab and the Imams after him used to curse the disbelievers in their Qunut (a type of supplication) during the prayer and otherwise. As for cursing a specific disbeliever, some scholars stated that it is not allowed to curse him, because we do not know how Allah will make his end. Others said that it is allowed to curse individual disbelievers. For proof, they mention the story about the man who was brought to be punished repeatedly for drinking (alcohol), a man said, "May Allah curse him! He is being brought repeatedly (to be flogged for drinking)." Allah's Messenger ﷺ said:
«لَا تَلْعَنْهُ فَإِنَّه يُحِبُّ اللهَ وَرَسُولَه»
(Do not curse him, for he loves Allah and His Messenger).
This Hadith indicates that it is allowed to curse those who do not love Allah and His Messenger . Allah knows best.