Is it permissible to request money from the ruler for construction purposes, given the suspicion that he acquired some of his wealth through unlawful means?

If the supplicant is someone for whom asking is permissible, or a person entitled to a share from the public treasury (Bayt al-Mal), then there is no harm in him asking the ruler to give him his need or the amount of his right. This is because if it is from the state's money and he is entitled to it, then there is no problem. And if it is from the ruler's personal wealth, which is mixed (with lawful and unlawful), then there is no harm in accepting his gift. Dealing with someone whose wealth is mixed is permissible according to the preponderant opinion, especially if the lawful portion is predominant.