Assalaamu alaikum!

Were the Prophet’s companion like Abu Bakr, Umar, Hamza, Khalid etc.. were circumcised when they embraced Islam? Is there any evidence about it? Is it obligatory for adult male reverts to circumcise? Please explain

Circumcision is a Sunnah for whoever embraces Islam. However, according to the opinion of the scholars who maintain its recommendation, circumcision is not considered a Sunnah if the person fears harm. Even the scholars who maintain its obligatoriness opine that it is impermissible to conduct the procedure if there is fear of harm. In such a case, circumcision must be delayed until the safety of the person is guaranteed since there is no worship in matters which may result in harm. And if some obligations are waived due to fear of incurring harm, then it is of greater precedence to waive recommended matters in similar cases as per the words of God Almighty, "And do not throw [yourselves] with your [own] hands into destruction." [Al-Baqarah, 195]