So I came across few of these Hadiths about selling/ransoming a human being.
Abu Sirma said to Abu Sa'id al Khadri (Allah he pleased with him):
O Abu Sa'id, did you hear Allah's Messenger (ﷺ) mentioning al-'azl? He said: Yes, and added: We went out with Allah's Messenger (ﷺ) on the expedition to the Bi'l-Mustaliq and took captive some excellent Arab women; and we desired them, for we were suffering from the absence of our wives, (but at the same time) we also desired ransom for them. So we decided to have sexual intercourse with them but by observing 'azl (Withdrawing the male sexual organ before emission of semen to avoid-conception). But we said: We are doing an act whereas Allah's Messenger is amongst us; why not ask him? So we asked Allah's Mes- senger (ﷺ), and he said: It does not matter if you do not do it, for every soul that is to be born up to the Day of Resurrection will be born. Abu Sirma said to Abu Sa'id al Khadri (Allah he pleased with him): 0 Abu Sa'id, did you hear Allah's Messenger (ﷺ) mentioning al-'azl? He said: Yes, and added: We went out with Allah's Messenger (ﷺ) on the expedition to the Bi'l-Mustaliq and took captive some excellent Arab women; and we desired them, for we were suffering from the absence of our wives, (but at the same time) we also desired ransom for them. So we decided to have sexual intercourse with them but by observing 'azl (Withdrawing the male sexual organ before emission of semen to avoid-conception). But we said: We are doing an act whereas Allah's Messenger is amongst us; why not ask him? So we asked Allah's Mes- senger (ﷺ), and he said: It does not matter if you do not do it, for every soul that is to be born up to the Day of Resurrection will be born.
The Hadith has been interpreted multiple times:
Muhairiz said “I entered the mosque and saw Abu Sa’id Al Khudri . I sat with him and asked about withdrawing the penis (while having intercourse). Abu Sa’id said We went out with the Apostle of Allaah(ﷺ) on the expedition to Banu Al Mustaliq and took some Arab women captive and we desired the women for we were suffering from the absence of our wives and we wanted ransom, so we intended to withdraw the penis (while having intercourse with the slave women). But we asked ourselves “can we draw the penis when the Apostle of Allaah(ﷺ) is among us before asking him about it? So we asked him about it. He said “it does not matter if you do not do it, for very soul that is to be born up to the Day of Resurrection will be born.”
Muwatta Malik Book 29, Hadith 95
Yahya related to me from Malik from Rabia ibn Abi Abd ar-Rahman from Muhammad ibn Yahya ibn Habban that Ibn Muhayriz said, "I went into the mosque and saw Abu Said al-Khudri and so I sat by him and asked him about coitus interruptus. Abu Said al-Khudri said, 'We went out with the Messenger of Allah, may Allah bless him and grant him peace, on the expedition to the Banu al-Mustaliq. We took some Arabs prisoner, and we desired the women as celibacy was hard for us. We wanted the ransom, so we wanted to practise coitus interruptus. We said, 'Shall we practise coitus interruptus while the Messenger of Allah, may Allah bless him and grant him peace, is among us before we ask him?' We asked him about that and he said, 'You don't have to not do it. There is no self which is to come into existence up to the Day of Rising but that it will come into existence.' "
There are other Hadiths as well beside intercourse with female captives while observing coitus interruptus:
Sunan Ibn Majah Vol. 3, Book 9, Hadith 1958
It was narrated from 'Aishah: that the Messenger of Allah (ﷺ) set Safiyyah free, and made her ransom her dowry, and he married her.
Some men of the Ansar asked for the permission of Allah's Messenger (ﷺ) and said, "Allow us to give up the ransom from our nephew Al-`Abbas. The Prophet (ﷺ) said (to them), "Do not leave (even) a Dirham (of his ransom).
Narrated Abdullah ibn Abbas:
The Prophet (ﷺ) fixed the ransom of the people of pre-Islamic Arabia at four hundred dirhams per head on the day of the battle of Badr.
So my question is, Does Islam allow human trafficking?
By human trafficking I meant to ask that you "acquire" a person either from war or trade & selling and ransom them for labor and sexual exploitation. Isn't that what you basically call human trafficking? Regardless of whether that person is a captive or prisoner, he/she is still a human being and Ashraful Makhluqat.