What is the ruling on someone who swore not to speak to a certain person, but then communicated with three friends online, knowing that he adheres to religious practices?

If by your statement, "If you speak to anyone, you will have committed Shirk (polytheism)," you intended to swear an oath to refrain from speaking on the internet, and that if you do speak, you will exit the fold of Islam, then this is forbidden and a grave sin. This is based on the Prophet's (peace be upon him) saying, "Whoever swears by a religion other than Islam, then he is as he said." You must repent from this reprehensible act.

As for your speaking with your friends after this oath, it depends on your intention. If you intended to exclude them, or to refrain from speaking for a specific period and then spoke after its expiry, then the oath is not broken. However, if you intended to stop speaking with everyone at all times, then you have broken your oath. Scholars have differed on the necessity of expiation in this case; the preponderant opinion is that it is not obligatory, but it is more cautious to offer it.

If you did not have a specific intention, then reference is made to what led you to take the oath. The apparent reason is the desire to avoid excessive use of the internet. Therefore, a fleeting question to friends does not fall under this, and the oath is not broken by it.