Wailing is prohibited. We will tackle it in a chapter of the Book of Prohibitions, Allah willing. As for weeping over the dead, there are many Hadīths that prohibit that and inform that the dead person suffers as a result of his family weeping over him. This is in case if the dead person had asked his family to do so. The prohibited weeping is the one that involves wailing and lamenting (crying out the merits of the deceased while), which is evidenced by many Hadīths, such as the following:
925/1 - Ibn ‘Umar (may Allah be pleased with him and his father) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) visited Sa‘d ibn ‘Ubādah during his illness. He was accompanied by ‘Abdur-Rahmān ibn ‘Awf, Sa‘d ibn Abi Waqqās, and ‘Abdullāh ibn Mas‘ūd. The Messenger of Allah (may Allah’s peace and blessings be upon him) began to weep, and when his Companions saw this, their tears also started flowing. He said: “Will you listen? Allah does not punish for the shedding of tears or the grief of the heart, but He punishes or bestows mercy because of this,” pointing to his tongue. [Narrated by Al-Bukhāri and Muslim]
1) It is permissible to weep over the dead, provided it involves no wailing.
2) A person’s feeling of mercy, softness of heart, and shedding tears when afflicted with calamity is something he is not to blame for.
3) It warns us of the danger of the tongue, as it is a means leading to earning Allah’s pleasure or wrath.
‘Nadb’ and ‘Niyāhah’ are prohibited.
‘Nadb’ means crying out the good traits of the deceased, by way of expressing discontent with Allah’s decree.
‘Niyāhah’ means wailing with long loud shrieks. The Prophet (may Allah’s peace and blessings be upon him) disassociated himself from the woman who does ‘Niyāhah’ over the dead.
926/2 - Usāmah ibn Zayd (may Allah be pleased with him and his father) reported that the son of the Prophet’s daughter was raised to him while dying, so his eyes flowed with tears. Thereupon, Sa‘d to him: “What is this, O Messenger of Allah?” He said: “This is mercy that Allah placed in the hearts of His slaves. Surely, Allah shows mercy to those of His slaves who are merciful.” [Narrated by Al-Bukhāri and Muslim]
1) Allah Almighty gives His servants recompense of the same nature of their actions. “Indeed, Allah shows mercy to those of His servants who are merciful.”
2) The more merciful a person is, the nearer he is to the mercy of his Lord.
3) We are urged to purify ourselves and train our souls to show mercy to those who deserve it.
927/3 - Anas ibn Mālik (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) entered upon his son Ibrāhīm while he was breathing his last. The Prophet’s eyes began to shed tears. ‘Abdur-Rahmān ibn ‘Awf said to him: “And you too, O Messenger of Allah?” He said: “O Ibn ‘Awf, this is mercy.” Then, he followed it by saying: “Indeed, the eye tears up and the heart is grieved, and we do not say except what pleases our Lord. And indeed, over your departure, O Ibrāhīm, we are grieved.”
[Narrated by Al-Bukhāri; partially narrated by Muslim]
There are many well-known authentic Hadīths in this area, and Allah knows best.
--
1) It is permissible for a person to say that he is sad over a certain affliction.
2) The Prophet (may Allah’s peace and blessings be upon him), the noblest human being in the sight of Allah, would go through what human beings go through, like sadness and illness.
3) Even if a person enjoys great status in the sight of his Lord, death is still not averted from him, for this is the decree of Allah, and it will surely come to pass.