That liveth in prosperity - The Hebrew is obscure, and is variously interpreted. The simplest rendering is, "And ye shall say thus about (his) life," i. e., with reference to his life, health, circumstances, etc.

Peace be both to thee - This is the ancient form of sending greetings to a friend: Peace to Thee, peace to thy Household, and peace to all that Thou Hast. That is, May both thyself, thy family, and all that pertain unto thee, be in continual prosperity!
Perhaps David, by this salutation, wished Nabal to understand that he had acted so towards him and his property that nothing had been destroyed, and that all had been protected; see 1-Samuel 25:15-17.

And thus shall ye say (c) to him that liveth [in prosperity], Peace [be] both to thee, and peace [be] to thine house, and peace [be] unto all that thou hast.
(c) Or, for salvation.

And thus shall ye say to him that liveth in prosperity,.... That lives, while others, as David and his men, might be rather said to starve than live; they lived in great meanness, but he in great abundance, and therefore in a capacity to give to others, and particularly to relieve them: or the sense is, they should say to him, "thus" shall it be, or may it be "for life": for the time of life, for the year to come; at this time next year, at next sheep shearing, mayest thou be in as great prosperity then as now, and even all the days of thy life:
peace be both to thee, and peace be to thine house, and peace be unto all that thou hast; that is, all prosperity to thy person in soul and body, to thy family, wife, children and servants, and let the same attend thy estate, cattle, farms, fields, vineyards, and all that belong to thee; and wish for a blessing on him, and his, and all that were his, or he had; a more extensive one could not well be made.

Prosperity - By this expression David both congratulates Nabal's felicity, and tacitly minds him of the distress in which he and his men were.