Is the monthly allowance the questioner has been receiving since the death of her first husband lawful or unlawful, given that she knows she remarried lawfully but did not register it civilly so as not to lose this allowance, and that she annually obtains a certificate of no marriage by false testimony? And what should she do?

It is not permissible to resort to deception to conceal a marriage and obtain a grant conditioned on the woman being unmarried. Repentance is obligatory, as is returning the grant or seeking absolution from its owners. The husband must spend on his wife in a reasonable manner, and she has the right to retract her waiver of her right to maintenance. If the husband is unable to provide sufficiently, then the relatives are obliged to cover her expenses in a reasonable manner, according to the prescribed legal order.