Change our intention

What happens if we were to change our niyyah while performing an action?

Ibn Rajab al-Hanbali says according to the ulama' if the niyyah at the end of the action matches the beginning (i.e. doing the action for the sake of Allah), then any changes in the middle of the action will be forgiven or does not matter, insha Allah.

However, if the niyyah at the end does not match the beginning, i.e. we do the action for other than the sake of Allah, then we must repent (taubah).