What is meant by "Then will come a people whose testimony precedes their oath, and their oath is their testimony"?

The phrase "the testimony of one of them precedes his oath, and his oath precedes his testimony" is part of a prophetic hadith found in the Two Sahihs (Bukhari and Muslim). Muslim's narration states: "The best of my Ummah are the generation that follows me, then those who follow them, then those who follow them. Then will come a people whose testimony will precede their oaths, and whose oaths will precede their testimony." Al-Nawawi mentioned that this is a dispraise for those who combine an oath with testimony. Some Malikis used this as an argument to reject the testimony of one who swears an oath along with it, but the majority of scholars do not consider it grounds for rejection. The meaning of the hadith is the combination of an oath and testimony, with one sometimes preceding the other.