He got his university certificate through an intermediary and got a job with it. What should he do?

Firstly: 

Getting your certificate through an intermediary when you did not deserve it is a haraam action, which involves a number of things that are forbidden. The one who intervened for you is a partner in the haraam action. The haraam actions which resulted from you obtaining this certificate through an intermediary are as follows: 

(a)

It was intercession for an evil cause. Allah says (interpretation of the meaning): 

“Whosoever intercedes for a good cause will have the reward thereof, and whosoever intercedes for an evil cause will have a share in its burden. And Allah is Ever All-Able to do (and also an All-Witness to) everything” [al-Nisa’ 4:85]

al-Haafiz ibn Hajar (may Allah have mercy on him) said: 

The reward for intercession is not general in meaning, rather it applies only to cases where the intercession is allowed, which is intercession for a good cause. That applies only to things which are allowed in sharee’ah, not to things that are not allowed, as indicated in this verse. Al-Tabari narrated with a saheeh isnaad that Mujaahid said: this applies to intercession of people for one another. To conclude, whoever intercedes for another in a good cause will have a share of the reward, and whoever intercedes for another in a false (bad) cause will have a share of the burden of sin."(Fath al-Baari, 10/451, 451)

(b)

It was deceit, because you submitted papers that were not valid. 

It was narrated from Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever deceives us is not one of us.” Narrated by Muslim, 102 

(c)

You pretended to be something that you are not – by claiming that you had obtained a certificate when that was not the case. 

It was narrated from Asma’ (may Allah be pleased with her) that the Prophet (peace and blessings of Allah be upon him) said: “The one who claims to have what he does not have is like one who wears two false garments (i.e., that do not belong to him).” 

Narrated by al-Bukhari, 4921; Muslim, 2130 

(d)

False speech and false testimony 

It was narrated that Abu Bakrah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Shall I not tell you of the worst of major sins?” We said: Yes, O Messenger of Allah. He said: “Associating anything with Allah, disobeying one's parents,” and he was lying down but he sat up and said: “And false speech and false testimony, and false speech and false testimony,” and he kept saying it until we wished that he would stop (out of compassion towards him).

Narrated by al-Bukhari, 5631; Muslim, 87. 

(e)

Lying to the bosses at work and to other people. 

It was narrated from Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “The signs of the hypocrite are three: when he speaks he lies, when he makes a promise he breaks it, and when he is entrusted with something he betrays (that trust).” Narrated by al-Bukhari, 33; Muslim, 59. 

(f)

Taking away the rights of others who had obtained genuine certificates without the intercession of anyone else. This is unjust towards those who were deprived of their right to a job. 

It was narrated from Abu Dharr (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) narrated that Allah, may He be blessed and exalted, said: “O My slaves, I have forbidden injustice to Myself and I have made it haraam among you, so do not be unjust towards one another.”

Narrated by Muslim, 2577. 

So you can see the seriousness of what you have done, since it involves so many sins and wrong actions. What you – and the one who interceded for you – have to do is to repent sincerely, by regretting what you have done, resolving not to do it again, praying for forgiveness and doing acts of worship. 

Secondly: 

With regard to your work and the money you have earned by having this certificate, we hope that your repentance will be sufficient to solve this problem, so long as you do your work well. 

See the answer to question no. 69820. 

And Allah knows best.