Allah tells us that after Ibrahim had calmed down from the excitement of this good news, he started to ask them why they had come to him. They said,
إِنَّآ أُرْسِلْنَآ إِلَى قَوْمٍ مُّجْرِمِينَ
(We have been sent to a guilty people.) meaning the people of Lut. They told him that they were going to save the family of Lut from among those people, except for his wife, because she was one of those who were doomed. Thus it was said,
(Except for his wife, of whom We have decreed that she shall be of those who remain behind.) i.e., she was one of those who would be left behind and will be destroyed.
Ma'arif al-Qur'an
Mufti Muhammad ShafiOn ayahs 48–71
From verse 48: لَا يَمَسُّهُمْ فِيهَا نَصَبٌ وَمَا هُم مِّنْهَا بِمُخْرَجِينَ (No weariness shall touch them therein nor will they be expelled from there), we learn about two features of Jannah: (1) No one shall ever feel tired or weak. This is contrary to what happens in our mortal world where hard work naturally results in fatigue. In fact, even a state of total rest and fun would sometimes tire a person out, no matter how enjoyable are things one is occupied with. (2) The other feature of Jannah we discover is that the blessings once received there shall be eternal. These blessings shall never diminish nor shall anyone be expelled from there. In Surah Sad, it was said:إِنَّ هَـٰذَا لَرِزْقُنَا مَا لَهُ مِن نَّفَادٍ (This is sustenance provided by Us which is never to exhaust - 38:54). And in the present verse, it was said: وَمَا هُم مِّنْهَا بِمُخْرَجِينَ (nor will they be expelled from there) that is, they shall never be deprived of the state of bliss bestowed upon them. This is contrary to the affairs of the mortal world where the recipient of the best of conveniences lives under the apprehension that the Over of the facilities may become displeased with him one of those days and expel him out.
Angels visited Abraham in the shape of human beings. In an exchange of questions and answers, they said that they had come with the command of God. What was this command for which the angels had come to Abraham? This was the good news of an extra-ordinary reward which could not be expected under ordinary circumstances. When God wants to confer an extraordinary benefit on man, He sends His special angel to him in order to accomplish the task. Angels of this kind come to prophets as well as to ordinary mortals. The difference is that when a prophet is visited by angels, he sees them and consciously grasps that those are angels, but ordinary men do not have this kind of certain knowledge or consciousness. However, the close proximity of angels may evoke unusual feelings in him. Such feelings can convey hints of the fact that at that time he is possibly in the company of the special angels sent by God.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.