Some years ago, a private tutor gave me a private course related to my study in the faculty in a certain place. I vowed that if I succeeded, I would give the tutor a certain present. At that time, I did not know the implications of making a vow. Moreover, I did not perform any act of worship, like prayer or supplication. I just did it by nature. Add to this that I do not know exactly where the tutor is now. What should I do in order not to be sinful?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If this present was intended to induce the tutor to give you grades that you did not deserve, for example, then this present is considered a bribe. Therefore, this vow is forbidden and it is prohibited for you to fulfill it. You should then offer an expiation like that of breaking an oath if you have actually succeeded.

However, if the present is given based on a valid intention, like to bring about love and friendship, then this is a Sharee'ah-approved intention, and you have to fulfill your vow if the condition was met—that being your success. If you can find that tutor, then give him the present. If you cannot find him, then you should offer an expiation like that of breaking an oath because your case is the same as that of someone who is not able to fulfill his vow.

We do not understand the meaning of your statement, "I did not perform any act of worship, like prayer…" If you mean that you had abandoned performing the obligatory prayers, then know that the prayer is the second pillar of Islam and  the first deed for which a Muslim will be reckoned. Thus, you should hasten to make up for all the prayers that you missed and continue to make up for them until you become almost certain that you have become free of liability.

Furthermore, abandoning fasting (the month of Ramadan) by someone who is required to fast by the Sharee'ah constitutes a huge act of disobedience. If you abandoned fasting in Ramadan after it had become obligatory upon you, then you have to make up for it for all the years in which you did not fast.

However, if you mean that you did not do any of these acts after making the vow as expiation for it, then we have already explained that you should fulfill the vow if you can. Otherwise, you should offer an expiation.    

Allaah Knows best.