The Ruling on Changing the Intention in Voluntary Prayer

Question:
What is the ruling on changing the intention in voluntary prayer? For example, if a person prays the greeting of the mosque and then changes his intention to make it the pre-prayer sunnah? Answer:

Answer:
One should not change the intention. A person should complete what he intended, except if he intended to pray a voluntary prayer and the call to prayer (iqamah) was made before he finished the second rak'ah, before the second bowing (ruku'). In that case, he must cut it off and invalidate it, based on the saying of the Prophet (peace and blessings be upon him)
As for changing the intention to the greeting of the mosque, and then intending it to be the regular voluntary prayer (rawatib) while he is in the middle of the prayer, that is not permissible. If he began the intention from the start of the prayer as the regular voluntary prayer, it suffices for the greeting of the mosque from the start of the prayer. However, if he did not intend it from the start of the prayer and entered it with the intention of the greeting, renewing the intention during the prayer does not benefit him, unless he cuts it off and intends it anew.