What is the meaning of "the Bestower (al-Mannan) who gives nothing except with a favor (minnah)" mentioned in a Sahih Muslim hadith?

"Al-mann" (to boast about one's generosity) is to mention a favor by way of enumeration and reproach, or to speak of what one has given to others in a way that harms them. It is one of the major sins that invalidate charity and nullify its reward and recompense. The one who does it is blameworthy and does not receive praise. Allah Almighty has praised those who spend and do not follow up their spending with boasting or harm, and He has threatened those who boast with painful torment, and that He will not look at them or purify them.