How is it to be presumptuous towards Allah by way of misrepresentation, and does its doer become an infidel, and is a person sinful if he does not know that what he said is forbidden?

"Ta'alli" (التألي) means to swear an oath. A servant's "ta'alli" against Allah is when they swear that Allah will not do something, such as saying: "By Allah, Allah will not forgive so-and-so." This indicates ignorance of Allah and bad manners towards Him, and it exposes the person to sin. It has been reported that woe be to those among the Ummah who engage in "ta'alli" by presuming to judge Allah, saying: "So-and-so is in Paradise and so-and-so is in Hell." There is no specific expiation for one who engages in "ta'alli," but they must offer sincere repentance and increase in acts of obedience and good deeds. Ignorance of the ruling may lift the sin from them.