Is it permissible for me to take the first name in an association I manage, which is designated for another person, without his knowledge, to meet my financial needs, and then pay him his share later?

It is permissible to participate in employee associations, a ruling issued by Sheikh Ibn Baz and affirmed by the majority of the Council of Senior Scholars, due to the benefit it entails. However, cheating in them is not permissible, as it constitutes forbidden deception and betrayal of trust. This is in accordance with the Almighty’s saying: "O you who have believed, do not betray Allah and the Messenger or betray your trusts while you know [the consequence]," and the Prophet's (peace be upon him) saying: "Whoever cheats us is not of us," and "Deceit and treachery are in the Fire."