A:
It is valid
for one performing an obligatory Salah to be led in praying by one performing a supererogatory Salah and vice versa. This is because
Mu‘adh (may Allah be pleased with him) used to perform Salah with the Prophet (peace be upon him) and then go back and lead his people in offering the same Salah, as reported in the Hadith agreed upon by Al-Bukhari and Muslim. The Prophet (peace be upon him) also once saw a man praying alone, so he (peace be upon him) said,
“Is there no man who will act charitably towards this (man) and pray with him?”
(Related by
Abu Dawud,
Al-Tirmidhy and
Ahmad) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.