Ruling on reserving a spot in the first row and staying away from it for a long time
Question

Is it permissible to observe i’tikaaf in the Prophet’s Mosque in the first row and to reserve the spot when going to sleep in the back of the mosque, then come back to the spot in the first row? Is it permissible to sleep in the first row when it is not the time for prayer?.
Praise be to Allah.It is permissible for one who is in the mosque to put his prayer mat etc in his spot, and to sleep at the back of the mosque, and then come back to his spot, even if that is in the first row, so long as the iqamah for prayer has not been given. If the iqamah for prayer has been given and he is not there, then he has no right to the spot and his prayer mat should be taken away. 
Similarly, if he goes out of the mosque for some reason, such as going to do wudoo’ and then comes back, he has more right to the spot. But if the reason is no longer present, and he is careless and comes back late, then he has no right to it. 
The evidence regarding this matter is the report narrated by Muslim (3179) from Abu Hurayrah (may Allah be pleased with him), according to which the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever gets up from his place then comes back to it, has more right to it.” 
Ibn Qudamah said in al-Mughni (2/101): 
If he sits in a place, then he leaves it because he wants to do something or he needs to do wudoo’, he may leave… If he gets up and leaves his spot then comes back, he has more right to it, because the Prophet (peace and blessings of Allah be upon him) said: “Whoever gets up from his place then comes back to it, has more right to it.” End quote. 
It says in Mataalib Ooli al-Nuha fi Sharh Ghaayat al-Muntaha (1/786): 
The one who comes back shortly after leaving for a reason such as wudoo’ has more right to the place where he was before than anyone else. If someone else has sat there, he has the right to make him get up… In al-Wajeez this was limited to cases where he comes back straightaway and is not distracted by anything else. End quote. 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said in al-Sharh al-Mumti’ (5/135) when discussing the prohibition on reserving a spot in the mosque then leaving the mosque: 
The correct view concerning this matter is that it is not permissible to reserve a spot and leave the mosque, and his prayer mat may be removed, because the basic principle is that whatever he put down with no right may be removed. But if negative consequences are feared as a result of picking it up, such as enmity or hatred and so on, then it should not be picked up, because warding off negative consequences takes precedence over bringing benefits. If Allah knows from your intention that were it not for this prayer mat you would be in his place, then Allah will give you the reward of those who sit in the front rows, because you only left this place in the front row for a reason. 
The phrase “so long as the time for prayer has not yet come” means that if the time for prayer has come and the iqamah has been given, then we may pick up the prayer mat, because in this case it has no sanctity or protection, and because if we leave it, there will be a gap in the row, and that is contrary to the Sunnah. 
An exception is made to the correct view that it is haraam to put down the prayer mat. If a man is in the mosque and he puts his prayer mat down in the first row, or anything else to indicate that he is reserving this spot, then he goes to the back of the mosque to sleep, or to read Qur’aan or another book, then in this case he is entitled to do that, because he is still in the mosque. But if the rows started to fill, then he has to go back to his spot, so that he will not be stepping over people’s necks. 
Another exception is that mentioned by the author:
Whoever gets up from his spot for some reason, then he comes back to it soon afterwards, he has more right to it. If a person has reserved a spot and he goes out of the mosque for a valid reason, then he comes back, he has more right to it. A valid reason is something like needing to do wudoo’, or if anything happens to him that makes him go out. If he goes out, when he comes back he has more right to it. 
But the author stipulated that he should come back quickly. The apparent meaning of the author’s words is that if he takes a long time to come back, he does not have more right to it, and anyone else may sit there. 
Some of the scholars said that he does have the right to it, even if he comes back after a long time, so long as the excuse was still in effect. This view is more correct, because the continuation of the excuse is like the beginning of it. If it is permissible for him to leave the mosque and to leave the prayer mat there when the excuse first appears, then if the excuse continues it is still permissible. But it is well known that if the iqamah for prayer is given and he is still absent, then his prayer mat should be picked up. 
It says in al-Rawd: The majority did not limit it to coming back soon, i.e., the majority of the companions of Imam Ahmad did not limit it to coming back soon, as is the apparent meaning of the hadeeth. 
But what we have mentioned is the middle view, i.e., that if he comes back after a long time because the excuse continued, then he has more right to it, but if the excuse ceased, but he was careless and took a long time, then he no longer has more right to it."(Al-Sharh al-Mumti’, 5/135)
There is nothing wrong with a person who is observing i’tikaaf sleeping in the first row in between the prayers, so long as that does not cause any annoyance or hardship to anyone else, in which case it is better to keep away from the front rows. 
It is preferable to avoid sleeping in the front rows out of consideration for other people, because they do not like this action. 
And Allah knows best.