Woman riding with a non-mahram man

What is the ruling on a woman riding with her sister’s husband in a car accompanied by her sister? Or riding with her husband’s brother accompanied by his mother?

 
May Allaah reward you greatly on our behalf, O Shaykh Muhammad, and join me with you and all the Muslims in Paradise for eternity.

Praise be to Allaah.  
With regard to clothes on which there are pictures, it is haraam to wear them for adults and children, males and females, alike.
With regard to a woman riding with a non-mahram man, one of the following two scenarios must apply.
1 – That she is riding on her own with him. This is the khulwah (being alone with a member of the opposite sex) which is forbidden. The Prophet (peace and blessings of Allaah be upon him) forbade it when he said: “No man is alone with a (non-mahram) woman but the Shaytaan is the third one present.” (Narrated by Ahmad and al-Tirmidhi in his Sunan, 2092; also inSaheeh al-Jaami’, 2546). 2 – That she is riding with a group of women and that non-mahram man. This is permitted, subject to two conditions:
(i)                That the man should be trustworthy
(ii)              That it should not be a journey, rather it should be inside the city. But if that is a lengthy journey then it is haraam for her to travel without a mahram, because the Prophet (peace and blessings of Allaah be upon him) said: “It is not permissible for a Muslim woman to travel the distance of one night’s travel without a man who is her mahram.” (Narrated by al-Bukhaari, 1088; Muslim, 1339. This version narrated by Muslim).
Based on that, it is permissible for a woman to ride with her sister’s husband if they are accompanied by her sister, and it is permissible for her to ride with her husband’s brother if they are accompanied by his mother, if there is no danger of fitnah.

Islam Q&A