Please preacher, is it biblically right to ask a person if he is customarily married or not, or whether he has two or more wives before such a person is baptized? If he fails any of the questions above, can you refuse to baptise such a person?
In many African nations there are two or more sets of marriage laws. The customary laws preserve the traditional marriage customs, most of which are contrary to Christ's Laws. For example, a person married under traditional customs is allowed to have multiple wives. This doesn't mean that a person married under the traditional customs is sinning. A person can ignore the aspects of the traditional customs, such as remaining married to just one woman.
Since traditional marriages are common in Africa, it would be necessary to discuss what being a Christian means in regards to a man's marriage and his future marriages. You will find some unwilling to submit to Christ's Law and thus refusing to get baptized. If a person has multiple wives, steps will need to be taken prior to baptism to end the marriages to the extra wives, even though he may need to continue supporting them financially.
The core is that having multiple wifes is adultery under Christ's Law. "And He answered and said to them, "Have you not read that He who made them at the beginning 'made them male and female,' and said, 'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'? So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate"" (Matthew 19:4-6). A person cannot become a Christian while clinging to the sins from which he claims he wants to be rescued. "What shall we say then? Shall we continue in sin that grace may abound? Certainly not! How shall we who died to sin live any longer in it?" (Romans 6:1-2). Baptism doesn't turn sins into righteousness. It breaks the chains of sin. "Knowing this, that our old man was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin. For he who has died has been freed from sin" (Romans 6:6-7).