What Women Should Do When the Man Leading Them in Prayer Invalidates His Ablution
21-9-2020 | IslamWeb
Question:
As-Salaam Alaykum. If one man is leading his female relative(s) in salah and his wudhu is invalidated, what should be done? Barakallah Feekum
Answer:
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.
If a person invalidates his ablution during the prayer, his prayer is invalidated, whether he is the Imam (leading the prayer), the one led in prayer, or praying by himself, and it is incumbent on him to repeat it.
In the case of the questioner’s situation, it is permissible for the women to complete their prayer individually. It is also permissible to appoint one of them to lead and complete the congregational prayer based on the fact that it is valid for a woman to lead other women in prayer according to the view of many scholars.
An-Nawawi 
said in Al-Majmoo': “Our companions (Shaafi‘i scholars) held that if the Imam leaves the congregational prayer abruptly due to a Hadath (state of ritual impurity, like passing urine, stool, or wind), whether it is done deliberately, involuntarily, out of forgetfulness, for some other reason, or without any reason, there are two known opinions regarding the permissibility of appointing another Imam to complete the congregational prayer. The new and correct of the two opinions in this regard is that it is permissible.” [End of quote]
Al-Mawsoo‘ah Al-Fiqhiyyah Al-Kuwaitiyyah reads: “The adopted opinion of the Hanafi scholars and the preponderant opinion of the Shaafi‘i scholars, which is the old adopted opinion of the Shaafi‘i school and one of two opinions attributed to Imam Ahmad, is that appointing another Imam to complete the congregational prayer is permissible. The outweighed opinion, according to the Shaafi‘i scholars and the other opinion of Imam Ahmad, is that it is impermissible. The Hanbali scholar Abu Bakr said: ‘If the Imam’s prayer is interrupted due to a non-deliberate Hadath which nullifies his ablution, his prayer and the prayer of those being led in the congregational prayer are invalidated accordingly, and this is the only opinion reported in this regard.’” [End of quote]
An-Nawawi said in Al-Majmoo’: “According to the scholars’ opinions regarding the congregational prayer for women, we have mentioned that our opinion is that it is recommended, whether the respective prayer is obligatory or voluntary. This opinion was reported by Ibn Al-Munthir on the authority of ‘Aa’ishah and Umm Salamah, ‘Ataa’, Ath-Thawri, Al-Awzaa‘i, and Ahmad.” [Summarized]
According to Haashiyat Ash-Shabraamallisi ‘ala Nihaayat Al-Muhtaaj, a Shaafi‘i book, while talking about appointing another Imam to complete the congregational prayer: “If the men being led in the prayer complete their prayers individually and the women appoint one of them to complete their congregational prayer, it is permissible … This is because it is permissible for them to complete the congregational prayer individually, and therefore it is permissible for them to complete the prayer in congregation with greater reason.” [End of quote, summarized]
Allah Knows best.