Answered by Shaykh Faraz Rabbani
With the understanding that any voluntary prayer is disliked after Fajr time enters. If fardh has been prayed and anyone arrives late: Can one join congregation with him? If one prays with the intention of rewards is it permissible? If one makes it for the intention of previously “missed salaah” is it acceptable?
Walaikum assalam,
It is prohibitively disliked to pray voluntary prayers after Fajr until the sun has risen. [Ala al-Din Abidin, Gifts of Guidance]
And it is not valid to perform a makeup prayer behind someone praying a current prayer [even if both are Fajr’].
Similarly, it is not valid to pray a makeup behind someone performing a makeup, unless both are making up the same prayer from the same day. [ibid.]
[For details, see the section on Prayer at http://www.sunnipath.com]
And Allah alone gives success.
Wassalam,
Faraz Rabbani