Sincere Repentance.
 

As-Salaam alaikum,
In ayat 8 of Surat Tahreem of the Holy Qur'an (66:8), it is stated:--

"O you who believe, truly turn to Allah with sincere repentance
[Taubatun Nasooha]: in the hope that your Lord will remove from
you your ills..."

What is sincere repentance? Sayyadi Abdullahi Ibn Abbas, may Allah be pleased with him, said that sincere repentance means that a person's heart is ashamed, his tongue seeks forgiveness and he resolves never to repeat the sin he or she committed.

And a certain wise man has mentioned that Allah's acceptance of Tauba (repentance) can be recognized by 4 signs as follows:--

(1) A person guards his tongue from futile talk, lying and backbiting.

(2) He habours no jealousy or enmity for anyone.

(3) He forsake evil company and

(4) He prepares for death, is always remorseful, always repenting and always obedient to Allah's Orders.