I am praying makeup prayers (Qadha) in the mosque when a tap my shoulder during 'Ishaa time thinking I'm performing Ishaa prayers. What should I do just continue my Qadha prayers or show signal not to follow me. Please explain in details.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

There is no harm for a person to take another praying person who is making up for missed prayers as an Imaam, thinking that he is praying the present prayer. The prayer is correct and the person who leads the prayer is not obliged to make the intention of leading the prayer.

Imaam An-Nawawi said: 'It is not a condition for the validity of being led in prayer that the person who is leading the prayer should have the intention of leading the prayer.' It does not matter whether the person who is taken as an Imaam started his prayer alone, or as leading the prayer, or was led in prayer and then became an Imaam, according to the correct opinion of the scholars.

So the brother asking the question is not obliged to explain to the person who wants to take him as an Imaam that he is praying a missed prayer.

Allaah knows best.