Question
What is the ruling for someone who intended to pray Fajr, then heard the Iqama from the nearby mosque and changed their intention to a voluntary prayer, then joined the congregational prayer with the intention of earning the reward of the congregation?
Answer
I say, and with God's success: It is permissible to change the intention for another prayer, as you have done, and then go to the mosque to catch the congregation, and God knows best.