Is it permissible for me to witness or conclude a marriage contract for a man and woman without knowing whether they perform Salah (Prayer) or not?
Please, bear in mind that most of the population of the region where the contract is concluded do not perform Salah. What will be the case if most of them perform Salah; should I ask about the status of the person marrying in particular regarding performing Salah? Answer us, may Allah reward you well!
Muslims are primarily thought of as just and punctual in performing Salah. Thus, if (Part No. 18; Page No. 184) you know nothing about him, you should primarily assume that he performs Salah and thus you may witness the marriage contract. However, if you know that he does not perform Salah while the wife does or vice versa, you may not witness the marriage contract as it will be null and void. The Prophet (peace be upon him) said,
I cannot bear witness to an injustice.
He (peace be upon him) also said,
That which differentiates us from them [disbelievers and hypocrites] is our performance of Salah. He who abandons it, becomes a disbeliever.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.