Praise be to Allah.
The hadeeth, “Whoever neglects prayer, Allah will send fifteen punishments upon him, six in this world, three when he is dying, three in the grave and three when he emerges from the grave…” is a fabricated (mawdoo’) hadeeth which is falsely attributed to the Messenger of Allah (peace and blessings of Allah be upon him).
Concerning this hadeeth, Sh. Ibn Baz (may Allah have mercy on him) said, in the magazine al-Buhooth al-Islamiyyah (22/329): With regard to the hadeeth which the author of this pamphlet attributes to the Messenger of Allah (peace and blessings of Allah be upon him) concerning the punishment of the one who does not pray, and which says that fifteen punishments will be sent upon him, etc., this is one of the fabricated ahadeeth (reports) that are falsely attributed to the Prophet (peace and blessings of Allah be upon him), as was stated by the scholars (may Allah have mercy on him) such as al-Hafiz al-Dhahabi in Lisan al-Meezan, and al-Hafiz ibn Hajar and others.
Similarly the Standing Committee issued a fatwa, no. 8689, declaring this hadeeth to be false, as it says in Fatawa al-Lajnah, 4/468. Among the things mentioned in this fatwa which it is worth quoting here are:
What has been narrated from Allah and from His Messenger (peace and blessings of Allah be upon him) concerning the punishment of the one who does not pray is sufficient. Allah says (interpretation of the meaning):
“Verily, as‑salah (the formal prayer) is enjoined on the believers at fixed hours.”
And Allah says of the people of Hell (interpretation of the meaning):
“‘What has caused you to enter Hell?’
They will say: ‘We were not of those who used to offer the salah (prayers).’”
And He mentioned among their attributes the fact that they did not pray.
The Prophet (peace and blessings of Allah be upon him) said: “The covenant that stands between us and them is prayer; whoever gives up prayer is a kafir (disbeliever).” Narrated by al-Tirmidhi, 2621; al-Nasai, 431; Ibn Majah, 1079. Classed as saheeh (authentic) by al-Albani in Saheeh al-Tirmidhi, 2113. And there are other verses and ahadeeth (narrations) which speak of giving up the prayer, and the Prophet (peace and blessings of Allah be upon him) described it as kufr (disbelief).
See also question no. 2182.
Al-Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: This hadeeth is mawdoo’ (fabricated) and falsely attributed to the Messenger of Allah (peace and blessings of Allah be upon him). It is not permissible to propagate it unless it is accompanied by a statement that it is fabricated, so that the people will have a clear understanding about it.
Fatawa al-Shaykh published by the Daw’ah center in ‘Anayzah, 1/6
We ask Allah to make you steadfast in your keenness to call your brothers and advise them, but you have to make it clear to everyone who is keen to do good for the people and to warn them against evil that it must be done in accordance with that which is proven from the Prophet (peace and blessings of Allah be upon him) and that there is sufficient material in the saheeh reports that we have no need for the da’eef (weak) material.
We ask Allah to grant you success and to guide those whom you call and all the Muslims to follow the straight path.
And Allah knows best.