Is it obligatory for one who has permitted something forbidden to declare what he has permitted after reciting the Shahada, or is an inward affirmation sufficient?

Whoever prohibits what is permissible or permits what is forbidden, when both are established and known to be indispensable parts of the religion, commits an act of disbelief; this is because it entails denying Allah and His Messenger, unless he is coerced, based on the Almighty's saying: "Whoever disbelieves in Allah after his belief - except for one who is forced [to renounce his religion] while his heart is secure in faith." The repentance of one who denies something known to be an indispensable part of the religion is by uttering the two testimonies of faith along with affirming what he had denied. Ibn Uthaymeen said: "As for the non-original disbeliever, he must repent from whatever caused him to be judged as an apostate, along with uttering the two testimonies of faith."