Is it permissible for a son to give a perpetual charity (Sadaqah Jariyah) on behalf of his deceased father from his own money, without a prior will from the father?

A son's initiative to establish an ongoing charity (Sadaqah Jariyah) from his own wealth for his deceased father is a good deed for which he will be rewarded, even if the deceased did not explicitly instruct it. The deceased benefits from the ongoing charity in his grave. Some scholars have explicitly stated that this is interpreted as an endowment (waqf) whose principal is preserved while its benefits continue to be enjoyed.