Answer
Wa `alaykum as-salam 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- You should try to find a person who has already done his obligatory Hajj and let him perform Hajj on her behalf.
2- All scholars agree on this: a person who does Hajj on behalf of another should have performed his own obligatory Hajj.
In responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada , states:
Ideally, according to all the scholars, a person who is performing Hajj on behalf of someone else must have performed Hajj on his own behalf first.
The Prophet (peace and blessings be upon him) told someone who was intending to perform Hajj on behalf of another relative that he should do so for himself first and then perform Hajj another time on behalf of his relative.
Therefore, I suggest that you find another person who has already performed Hajj to perform it on her behalf, rather than send your brother-in-law.
Having said this, however, I must say that it may not be considered haram for your brother-in-law to do this – if he is financially ineligible to perform Hajj – to do this on behalf of your mother-in-law, especially if you cannot find anyone else to do it.
Allah Almighty knows best.
Editor’s note: This fatwa is from Ask the Scholar’s archive and was originally published at an earlier date.