Assalaamu alaykum wa rahmatullaahi wa barakaatuhu. I am a 21-year-old girl. My mother is Christian, and my father is Muslim. I converted to Islam when I was 16, but my sister, who is 23 years old, is atheist. My sister had a hidden relationship with a 31-year-old married man who has 2 children and whose wife is pregnant. When she asked me what she should do, I told her that she should end it. She, however, continued with it. After some months, she got pregnant, and she only told me two months later because she was afraid of my reaction. That man and she decided to abort the fetus, and she asked me for my opinion. I searched whether it is Islamically okay to do so after two months or not, and I found different opinions; one of them was that it is permissible till the fourth month, so I told her that I think that she can do it (only to give her the right advice). She told me not to tell our parents anything about it, but I did tell them because I thought it is better to collaborate with them than with her, and I also thought that they could provide a better solution to this problem. So instead of lying to my parents, I lied to my sister, but it was only for her good. Till now, she knows nothing about that and ignores how my parents discovered this. My question is: was abortion the best thing to do? Did I give the right advice? Was it good to lie to her? I am worried about that, because it is an enormous responsibility. May Allaah reward and bless you.

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, sallallahu ‘alayhi wa sallam, is His slave and Messenger. 

First of all, we would like to congratulate you for Allah's favor upon you by having guided you to Islam. We ask Allah to bless you with steadfastness on the truth unto death. We advise you to take care of your mother and sister and be kind to them; perhaps Allah would make you a reason for blessing them with what He blessed you with, for which you would receive a great reward. Sahl ibn Sa‘d, may Allah be pleased with him, narrated that the Prophet, sallallahu ‘alayhi wa sallam, when he sent ‘Ali ib Abi Taalib to Khaybar, said, “...And invite them to Islam and inform them of what Allah has enjoined upon them. By Allah! If a single person embraces Islam at your hands, that will be better for you than the red camels (meaning the most precious possessions).” [Al-Bukhaari and Muslim] Your dutifulness towards your mother and kindness towards your sister are the most effective means to guide them to Allah, as it reflects the goodness and tolerance of Islam.

The ruling on abortion is as you have read; scholars held different views regarding it. You bear no sin for telling your sister what you said; however, we believe that abortion is not the optimal solution, because the preponderant view to us is that abortion is prohibited at any stage of the fetus. Please, refer to fatwas 101103 and 153815. Moreover, having the choice to have abortions may make your sister take the matter of adultery lightly and thus embolden her to continue sinning.

Disclosing a secret is Islamically prohibited, especially if the person who confided in you asked you not to disclose it. However, there is no harm in disclosing the secret if that yields a guaranteed benefit, such as the case with revealing your sister's secret so that your parents could do their duty towards her; so there is no harm in disclosing your sister's secret to them in this situation. Al-Haafith Ibn Hajar cited in his commentary on a hadeeth narrated by Al-Bukhaari and Muslim that Bilaal, may Allah be pleased with him, disclosed the secret of the wife of Ibn Mas‘ood and a woman from the Ansaar to the Prophet, sallallahu ‘alayhi wa sallam, when they asked him to ask the Prophet about something without telling him that it was the two of them who were asking. When the Prophet, sallallahu ‘alayhi wa sallam, asked Bilaal for the names of the questioners, he told him who they were.

Allah knows best.