All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If a non-Muslim who has uttered the Shahaadatayn (The Two Testimonies of Faith – which is to say –which is to say: Ash-hadu an La Ilaaha Illa Allah wa Ash-hadu anna Muhammadan Rasoolu Allah; meaning: I bear witness that there is None worthy of worship but Allah and I bear witness that Muhammad is his Messenger), knows the rulings of the Sharee’ah and does not follow them though he is able to implement them, then he is not considered a Muslim since he lacks one of the main conditions of being Muslim; i.e., following the Islamic Sharee’ah.
Therefore, the marriage with this mentioned person is not valid since he still did not accept Islam in real. So, we advice you to cut off all relations with him until he proves his true adherence to Islam.
We draw your attention to the fact that it is your responsibility to teach the rulings of Islam to every new Muslim you get in contact with or guide him/her to the closest Islamic centers. The authorities in those centers may surely try to explain to this new Muslim the religion and encourage him/her to follow the rulings of Sharee’ah.
However, you have to cut off all your relations with this person to avoid the prohibitions you might commit otherwise. If you cut off your relations with him, you are not considered as a sinner; rather, you will be rewarded for doing a good act. On the other hand, you must seek a religious husband who can help you in following the Sharee’ah and in being steadfast.
If this person accepts Islam willingly and follows the rulings of the Sharee’ah seriously; then, in this case, you may marry him, but it is not advisable to await his becoming steadfast; probably you may expose yourself to some prohibitions while you are waiting for him.
No doubt, if he becomes a true Muslim and gets the guidance through you, it is a good achievement since the Prophet said: “I swear by Allah! If Allah guides one single man (to Islam) by your efforts, that will be better for you than possessing an abundant number of red camels (a very expensive breed of camels which is considered as the most valuable property in the sight of the Arabs).” [Al-Bukhari and Muslim]
As for the means that will help you to become steadfast, they are as follows:
Performing prayers regularly and reciting the supplications continuously. You may find authentic supplications in many Islamic websites. In addition, you should befriend good pious Muslim ladies, keep on reciting the Quran, memorizing it, and listening to the cassettes of Quranic recitation. Spend your time in reading useful books, avoid bad places as well as bad friends.
Allah knows best.