He wants to do ‘umrah on behalf of someone who has been missing for four years, and he is asking about the ruling on doing ‘umrah on his behalf; will the one who does ‘umrah or Hajj on his behalf be rewarded?
Question

My question has to do with ‘umrah in Ramadan, as I am going to do ‘umrah soon, and I hope that you can answer my question. The father of a friend of mine in Syria, in Damascus, disappeared four years ago, and we have had no news of him. We have spent the last four years looking for him and asking about him, with no success until now, no trace of him and no news. My questions are: 1. Can we assume that my friend’s father has died? What are the rulings once it is assumed that someone who has disappeared is dead? 2. Is it permissible for me to do ‘umrah on his behalf? 3. Will we both receive the reward of ‘umrah in Ramadan, which is equivalent to Hajj, in sha Allah? Or is it only me that will attain this reward?
Praise be to Allah.Firstly:
If someone is lost and disappears to the extent that it is not known whether he is alive or dead, then he may be deemed to have died after the passage of a certain length of time, when it becomes most likely that if he were still alive, you would have heard news of him by now.
The most correct view regarding the definition of this period is that reference should be made to the qaadi (shar‘i judge). The qaadi is the one who should define what that time period is, because the circumstances of those who go missing and the causes that led to their disappearance vary greatly.  So the case of each missing person should be examined by the qaadi in order to determine the most appropriate period in light of the incident that led to his disappearance.
See the answer to question no. 226048 .
In the case of this man who is missing in Syria, if he went out of his house as normal and did not return for four years, then in this case it is most likely that his absence is due to his having died.
But because of the complicated circumstances and situation of people in Syria, and because of the seriousness of the rulings that result from deeming him to have died, no one should determine that he has died except the qaadi.
Shaykh Ibn ‘Uthaymeen said, regarding the issue of one who is missing:
It is essential to have the ruling of a qaadi, to avoid causing chaos among people, because if we say that every woman whose husband has gone missing should wait for a certain length of time until she thinks it most likely that he has died, then she may remarry, that would lead to chaos.
It is essential to consult the qaadi, for he is the one who should handle this matter, and this is a must." (Ash-Sharh al-Mumti‘  13/374).
If there is a qaadi (shar‘i judge) in your area, then he should be consulted to rule concerning this matter.
If there is no qaadi or it is not possible to contact him, then the scholars in your area should act in the stead of the qaadi, because it is a matter of necessity. So one of the trustworthy scholars may rule concerning that, who is qualified to issue fatwas concerning such matters, and his ruling will be binding, like the ruling of the judge.
Ad-Dasooqi al-Maaliki (may Allah have mercy on him) said:
Note regarding some issues connected to the missing person: his marriage may be annulled because of his not spending on his wife’s maintenance or because his wife is harmed because of the empty bed. But his marriage can only be annulled by a qaadi, unless it is difficult to find a qaadi either in a real sense are in a metaphorical sense, such as if the qaadi insists on charging to annul the marriage, in which case a group of Muslims may act in his stead, as was mentioned by our shaykh al-‘Adawi." (Haashiyat ad-Daasooqi  3/302).
Secondly:
With regard to the rulings that result from the determination that the missing person has died, there are many rulings, the most important of which are:
His wealth should be divided among his heirs if the qaadi rules that he has died.
His wife should observe the ‘iddah of one whose husband has died, from the time it is determined that he has died. After her ‘iddah ends, she may remarry if she wishes.
See the answer to question no. 214999 .
With regard to doing ‘umrah on behalf of this missing person, there is nothing wrong with doing ‘umrah on his behalf, even if the judge has not determined that he has died, because doing an act of worship on behalf of someone else, or dedicating the reward of that to him, is not a transgression against any of the rights of the missing person, or any of his relatives, so it is not taking away someone’s rights or neglecting someone’s rights, and it is not a matter to be strict about. The matter is broad in scope, praise be to Allah.
See the answer to question no. 228060 .
Thirdly:
If someone does ‘umrah or Hajj on behalf of someone who is deceased or incapacitated, will he have a similar reward, or is the reward only for the one on whose behalf it was done?
There are two scholarly views concerning this matter, as the texts concerning it are not clear.
Whatever the case, undoubtedly the one who does that on behalf of someone else will be rewarded for showing kindness to his brother by doing the rituals on his behalf, and he will be rewarded for whatever he does of acts of worship that are separate from the actions of Hajj, that he does in the Haram, such as prayer, dhikr, du‘aa’, and so on.
With regard to any reward in addition to the reward for that, that is subject to Allah’s will, and Allah’s bounty and kindness are immense.
For more information, please see the answer to question no. 174707 .
And Allah knows best.