(Proclaim their real parentage) name them in relation to their real fathers. (That will be more equitable) better, more correct and fairer (in the sight of Allah) in relation to lineage. (And if ye know not their fathers) if you do not know the lineage of their fathers, (then (they are) your brethren in the faith) name them with names showing brotherhood in faith: 'Abdullah, 'Abd al-Rahman, 'Abd al-Rahim and 'Abd al-Raziq, (and your clients) and name them as your clients. (And there is no sin for you in the mistakes that ye make unintentionally) regarding the identification of one's parentage, (but what your hearts purpose (that will be a sin for you)) what is a sin for you is to attribute intentionally someone to other than his real father. (Allah is Forgiving) of what was done in the past, (Merciful) in relation to what will happen in the future. This verse was revealed about Zayd Ibn Harithah who was adopted by the Prophet (pbuh). People used to call him Zayd Ibn Muhammad, but Allah forbade them from calling him so and guided them to what is proper.