A Monotheist at the time of Jahiliyyah
He was Zaid ibn Amr May Allah have mercy on him
a) Narrated ‘Abdullah Ibn ‘Umar (رضي الله عنه): The Prophet (ﷺ) met Zayd Ibn ‘Amr Ibn Nufail in the bottom of (the valley of) Baldah before any Wahy (Divine Inspiration) came to the Prophet (ﷺ). A meal was presented to the Prophet (ﷺ) but he refused to eat from it. (Then it was presented to Zayd) who said, “I do not eat anything which you slaughter in the name of your stone idols. I eat none but those things on which Allah’s Name has been mentioned at the time of slaughtering.” Zayd Ibn ‘Amr used to criticise the way Quraish used to slaughter their animals, he used to say, “Allah has created the sheep and He has sent the water for it from the sky, and He has grown the grass for it from the earth; yet you slaughter it in other than the Name of Allah.” He used to say so, for he rejected that practice and considered it as something abominable. [Al-Bukhari: 3826].
b) Narrated Asma bint Abi Bakr (رضي الله عنها): I saw Zayd Ibn ‘Amr Ibn Nufail standing with his back against the Ka’bah saying, “O people of Quraish! By Allah, none amongst you is on the Religion of Ibrahim (عليه السلام) except me.” He used to preserve the lives of little girls: If somebody wanted to kill his daughter he would say to him, “Do not kill her for I will feed her on your behalf.” So he would take her, and when she grew up nicely, he would say to her father, “Now if you want her, I will give her to you, and if you wish, I will feed her on your behalf.” [Al-Bukhari: 3828].
c) When Zaid ibn Amr went to Jews and Christians to inquire about true religion, He was not satisfied and prayed to Allah by saying “O Allah! I make You my Witness that I am on the religion of Abraham.” [Sahih al-Bukhari 3827]
d) Prophet peace be upon him said: He will come on the day of judgement like one Ummah. [al Mustadrak al Hakim no. 4956, Sh Zubair Ali Zai said: The chain is Hasan and authenticated by al Hakim on the sharait of Muslim and ad-Dahabee agreed with him in at-Talkhees, see his tahqiq of Fadaail as-Sahaba page 76]
Hafidh Sher Muhammad (student of Shaykh Zubair Ali Zai) said “Saeed bin Zaid`s RadhiAllahanho father Zaid bin Amr bin Nufayl was on Tauheed and on Deen e Ibraheem , He died before any Revelation came to the Prophet (ﷺ). [Fadail as-Sahaba page 75]