Question Summary:
Is it necessary to uphold an oath taken regarding sensitive secret information whereas such information would leak out later?

Question Detail:

Someone approached regarding sensitive information and made us take an oath that we would not act on this due to its nature. 

We asked him if it related to certain topics and he assured us it did not. We took the oath thinking that it was some information which would allow us to assist someone or at least know not to come close to the topic with that person. 

After we had taken the oath, he told us the information but it was clear then that he had anterior motives. The information was such information that would have come out in public and was neither secret not sensitive. 

We were told to make this oath only to prevent us from what would have been our normal course of actions on information which would have been found out by us in any instance. 
Is this oath valid?

If the oath is valid, what penance do we have to pay for breaking the oath?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
Upholding of oaths is an emphasized injunction of Shari’ah. Allāh says:
وَاحْفَظُوْا أيْمَانَكُمْ [1]
“Safeguard your oaths”
Therefore, it is incumbent upon you to refrain from taking any action in relation to the information disseminated to you, regardless of whether the information becomes public or not. However, if there is any Deenī benefit in acting contrary to your oath, then you may break the oath and act accordingly. In such a scenario, you will have to give Kaffarah (expiation) for breaking your oath. [2]
The Kaffarah (expiation) for an affluent person is to feed ten needy individuals two meals or to provide ten needy individuals with clothing.[3] Alternatively, instead of feeding ten individuals two meals, one may give each one of the ten individuals cash equivalent to the amount of Sadaqah Fitr.[4] As for one who is incapable of doing this due to financial constraints, then he/she should fast for three days.
 
And Allah Ta’āla Knows Best
Nabeel Valli
Student Darul Iftaa
Lusaka, Zambia
Checked and Approved by,
Mufti Ebrahim Desai.
www.daruliftaa.net