Rulings on sins committed against other people before being guided
Question

                A person was ignorant, then Allaah blessed him with Islam. Before that, he used to commit some sins. He says, “I heard a hadeeth of the Messenger of Allaah (peace and blessings of Allaah be upon him), ‘Whoever has wronged his brother with regard to his honour or anything else, let him ask him for forgiveness today before there is no dinar and no dirham.’ What do you advise me to do?”
Praise be to Allah.Allaah has enjoined repentance 
          upon His slaves, as He says (interpretation of the meanings):  
          
“And all of you 
          beg Allaah to forgive you all, O believers, that you may be successful” 
          
[al-Noor 24:31]  
“O you who believe! 
          Turn to Allaah with sincere repentance!” 
[al-Tahreem 66:8]  
“And verily, I 
          am indeed forgiving to him who repents, believes (in My Oneness, and 
          associates none in worship with Me) and does righteous good deeds, and 
          then remains constant in doing them (till his death)” 
[Ta-Ha 20:82]  
And the Prophet 
          
          (peace and blessings of Allaah be upon him) said: “The one who repents 
          from sin is like one who has never sinned.”  
Whoever commits any sin 
          must repent, regret what he has done, give it up, keep away from it 
          and resolve not to go back to it. Allaah accepts the repentance of those 
          who repent.  
When a person sincerely 
          repents by regretting what he has done and resolving not to repeat it, 
          and he gives it up out of respect and fear of Allaah, then Allaah accepts 
          his repentance and wipes out his past sins by His grace and kindness.  
          
But if the sin involved 
          wrongdoing against someone else, then the sinner has to do what he is 
          obliged to do by repenting from what has happened, regretting it, giving 
          it up and resolving not to do it again. He must also restore the rights 
          of the one whom he wronged, or seek his forgiveness , such as saying, 
          Please forgive me,” etc. Or he should give him his dues, because of 
          the hadeeth quoted in the question, or other ahaadeeth and aayahs. The 
          Messenger 
          
          (peace and blessings of Allaah be upon him) said: “Whoever has done 
          some wrong to his brother, let him seek his forgiveness today before 
          there is no dinar or dirham, when if he has some righteous deeds (to 
          his credit), some of his hasanaat (good deeds) will be taken in proportion 
          to his wrongdoing, and if he has no hasanaat some of the sayi’aat (bad 
          deeds) of the one whom he wronged will be taken and added to his burden.” 
          (Narrated by al-Bukhaari in his Saheeh). So the believer should 
          strive to put things right and restore his brother’s rights. So he should 
          either give him his dues or ask him for his forgiveness. If it has to 
          do with his honour then he has to ask for his forgiveness if he can. 
          If he cannot, or he fears the consequences of telling him or that telling 
          him about what he said will cause more trouble, then he should pray 
          for forgiveness for him and make du’aa’ for him, and mention his good 
          points that he knows of , to compensate for saying bad things, aiming 
          to wash away something bad with something good. So he should speak of 
          his good points that he knows of and spread good words about him to 
          counteract the bad things which he said before, and he should pray for 
          forgiveness for him and make du’aa’ for him. In this way the problem 
          will be solved.