What is the ruling on praying behind an Imam who doubts whether he fully washed his hands during ablution?

Washing the hands in wudu (ablution) is obligatory from the fingertips to the elbows, and it is not permissible to limit it to washing the wrists. This is the view of the majority, contrary to the Hanafis. Nevertheless, prayer is valid behind a Hanafi who suffices with washing the hands (palms) and then the forearms, because it is a matter of scholarly difference, and a layman is excused for following scholars. Prayer is also valid behind someone whose condition you do not know, and the Muslim's condition should be assumed to be sound. This issue should be explained to your brothers with wisdom, and if they insist on their opinion, there is no harm in praying behind them, for imams have always prayed behind each other despite their differences in subsidiary matters. Ahmad explicitly stated the validity of praying behind those who differ in subsidiary matters, such as the followers of Abu Hanifa, Malik, and Al-Shafi'i, because the Companions and the Tabi'un used to pray behind each other despite their differences. If the imam omits a pillar or condition that the follower believes in but the imam does not, then the apparent meaning of Ahmad's words is the validity of praying behind him as long as he has an interpretation.