Is it valid to pray that the angels will offer supplication for a person if he repents, and the angels will say: O Allah, make him rejoice as he has made us rejoice?
Question

How sound is this supplication: “When a person repents, the angels say: O Allah, make him rejoice as he has made us rejoice, and they say:  As he has made us rejoice and has repented, then – O Lord – make him rejoice, and Allah will cause  His slave to rejoice in Paradise”?
Praise be to Allah.The world of the pure angels is one of the matters of the unseen, which it is not permissible to speak about except on the basis of a text from the Holy Qur’an or a report that was soundly narrated from the Prophet (blessings and peace of Allah be upon him).
What the questioner has quoted about the angels saying when someone repents, “O Allah, make him rejoice as he has made us rejoice,” has no basis, and it was not mentioned by any of the scholars with any isnaad at all, or even without an isnaad.
The first one we have come across who mentioned it is one of the contemporary daa‘iyahs in a series of his about the hereafter, but he did not mention any isnaad for it, and he did not attribute it to anyone.
What is proven in the saheeh Sunnah is that Allah rejoices at the repentance of His slave when he repents to Him.
This hadith was narrated from a number of the Sahaabah, including Anas, Abu Hurayrah, ‘Abdullah ibn Mas‘ood, an-Nu‘maan ibn Basheer, and al-Bara’ ibn ‘Aazib (may Allah be pleased with him).
The hadith of Anas was narrated by al-Bukhaari in his Saheeh (6309) and by Muslim in his Saheeh (2747): Anas (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Allah rejoices more over the repentance of His slave when he repents to Him than one of you who was on his mount in the wilderness, then he lost it, and his food and drink are on it, and he despairs of finding it. He goes to a tree and lies down in its shade, having lost hope of finding his mount, and whilst he is like that, there it is standing in front of him, so he takes hold of its reins and says, because of his intense joy, ‘O Allah, You are my slave and I am your lord,’ making this mistake because of his intense joy.”
There can be no doubt that the angels, likewise, rejoice when someone repents to his Lord, because Allah rejoices at that.
Ibn Abi Hamzah said in Bahjat an-Nufoos (1/202): The angels rejoice at the righteous deeds of people. End quote.
It is proven that the noble angels pray for forgiveness for the one who repents to Allah, may He be exalted.
Allah, may He be blessed and exalted, says (interpretation of the meaning):
{Those [angels] who carry the Throne and those around it exalt [Allah] with praise of their Lord and believe in Him and ask forgiveness for those who have believed, [saying], “Our Lord, You have encompassed all things in mercy and knowledge, so forgive those who have repented and followed Your way and protect them from the punishment of Hellfire”} [Ghaafir 40:7].
As explained above, there is no basis for this supplication which is attributed to the angels.
And Allah knows best.