What is meant by "abandoning clothing" in the prophetic Hadith: "Whoever abandons clothing out of humility to Allah while he is able to afford it, Allah will call him on the Day of Resurrection before all creatures until He gives him the choice to wear whichever of the garments of faith he wishes"? Does this include expensive clothing, and what is the controlling factor in that?

What is meant by "abandoning clothing" in the Hadith is: refraining from wearing expensive clothes out of humility towards Allah, even when one can afford them. The reward for this is that Allah will give him the choice on the Day of Resurrection to wear any of the garments of faith he wishes.

This does not generally mean dispraising good clothing, for the Prophet, peace and blessings be upon him, used to wear and adorn himself, and Allah is beautiful and loves beauty.

Balance is required; a Muslim wears what suits his situation and environment. If he is among those of average means, humility is more befitting. If he is among the well-off, wearing good clothes is more befitting, to show the effect of Allah's blessings upon him, and to avoid clothes of ostentation.