Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- If the marriage contract is concluded, then one of the spouses dies before consummation of the marriage, spouses inherit from one another.
2- The wife is obliged to observe the iddah (waiting period) of one whose husband has died which is four months and ten days.
Answering your question, the Fatwa Center at Islam Q and A, states:
If the marriage contract is concluded, fulfilling all the necessary conditions, then one of the spouses dies before consummation of the marriage, the marriage contract remains in effect and spouses inherit from one another. This is because of the general meaning of the verse in which Allah says:
“And for you is half of what your wives leave if they have no child. But if they have a child, for you is one fourth of what they leave, after any bequest they [may have] made or debt. And for the wives is one fourth if you leave no child. But if you leave a child, then for them is an eighth of what you leave, after any bequest you [may have] made or debt.” (An-Nisaa’ 4:12)
The verse is general in meaning and is applicable to the woman whose husband dies before or after consummation of the marriage.
With regard to the iddah (waiting period), the wife is obliged to observe the iddah of one whose husband has died even if her husband who did the marriage contract with her dies before consummation of the marriage.
In that case, she must observe iddah like any other widow, because of the general meaning of the verse in which Allah says:
“And those who are taken in death among you and leave wives behind – they, [the wives, shall] wait four months and ten [days].” (Al-Baqarah 2:234)
This includes both the one whose husband dies before consummation of the marriage and the one whose husband dies after consummation. (Al-Muntaqa min Fatawa Ash-Shaykh Salih al-Fawzan, 3/135)
Abu Dawud narrated that Ibn Mas`ud (may Allah be pleased with him) was asked about a woman whose husband died before consummation of the marriage, and he had not specified a dowry for her. He said: She is entitled to the dowry in full, like that of her peers; she must observe iddah and she is entitled to inheritance. Ma`qil ibn Sinan (may Allah be pleased with him) said: I heard the Messenger of Allah (peace be upon him) issue the same verdict as you concerning Barwa` bint Washiq, one of our women. (Classed as sahih by Al-Albani in Irwa’ al-Ghaleel, 1939)
Almighty Allah knows best.
Source: www.islamqa.info