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.
For a revocable divorced woman, it is permissible for her husband to take her back as long as she is in the period of 'Iddah (waiting period). It is sufficient for the validity of taking her back that the husband says to his wife: “I take you back as my wife”, for example, and the like. Thus, it is valid for a husband to take his wife back verbally by agreement of scholars.
In addition, intercourse is not required for the validity of taking one’s wife back; rather, it is valid even without intercourse.
We point out to the two following matters:
The first matter: the spouses should be keen on avoiding the causes of dispute and not leave a chance for the devil to spoil the cordiality between them and cause discord. Also, they should both be wise in resolving a dispute if it occurs; divorce is not always a beneficial solution, nor is it always the best.
The second matter:
We advise your husband to strive hard to find a cure for impotence by consulting specialized doctors, while supplicating a lot and asking Allah for success.
Allah knows best.