Rather, it was only a handful of scholars who considered prompting the deceased after burial to be recommended, and—so far as we know—they have no reliable proof from the Messenger of Allah ﷺ. Accordingly, prompting after burial has no foundation in the Sunnah of the Messenger ﷺ; it was merely the result of some scholars’ independent legal reasoning (ijtihād). Every person’s statement may be accepted or rejected except that of the Messenger of Allah ﷺ. Thus, we accept from a mujtahid whatever is supported by evidence and leave whatever is unsupported.
With regard to your question about the Prophet ﷺ allegedly prompting his son Ibrāhīm, I have found no basis for this either, and it appears to have no foundation at all. How could the Prophet ﷺ have prompted Ibrāhīm when the child died very young, before any religious obligations were binding upon him? This, in itself, shows that the report has no basis in the Sunnah of the Messenger ﷺ.
In sum, it is incumbent upon the Muslim to return to the truth even if others disagree with him, and to abandon whatever lacks evidence—even if some people practice it—because we are obliged to follow the proof and to follow what the Messenger ﷺ brought, not to adopt uncritically whatever we find people doing without first examining it against the Book and the Sunnah. This is my advice to you and to my fellow Muslims: prompting after burial has no basis in the Sunnah. The only legislated prompting is at the moment of death, for that is what benefits the dying person and what he can comprehend; he is still alive, able to utter the testimony of faith, and still in the realm of action—this worldly life, which is the arena of deeds. After death the time for action ceases, his record is sealed, and he moves on to another abode. Allah knows best.
Question: After the deceased has been placed in his grave, is it not prescribed—or at least recommended—to supplicate for him and to ask that he be made steadfast, as the Messenger ﷺ instructed in some hadiths?