C. F. Keil and Franz Delitzsch on 2 Samuel 20:3

2Sa 20:3

As soon as David returned to his palace at Jerusalem, he brought the ten concubines whom he had left behind, and with whom Absalom had lain, into a place of safety, and took care of them, without going in unto them any more. The masculine suffixes attached to יתּגם, יכלכּלם, and אליהם are used, as they frequently are, as being the more general and indefinite, instead of the feminine, which is the more definite form. Thus were they shut up in lifelong widowhood until the day of their death. אלמנוּת is an adverbial accusative, and חיּוּת signifies “condition in life;” literally, in widowhood of life.