There is nothing wrong with offering supplication for others, even if it is on condition that they do something, such as saying: O Allah, forgive whoever watches this video, and the like. In the Sunnah there are examples of offering supplication for those who do a certain action, such as when the Prophet (blessings and peace of Allah be upon him) said: “May Allah make radiant the face of a man who hears something from us and conveys it as he heard it, for perhaps the one to whom it is conveyed may understand it better than the one who heard it directly.” Narrated by at-Tirmidhi (2657), Abu Dawud (3660) and Ibn Majah (230). Al-Albani classed it as sahih in Sahih at-Tirmidhi.
Al-Bukhari (2076) narrated from Jabir ibn ‘Abdillah (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “May Allah have mercy on a man who is easy going when he sells and when he buys and when he asks for a debt to be paid to him.”
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