Smith's Bible Dictionary (1863)
The first day of the lunar month was observed as a holy day. In addition to the daily sacrifice there were offered two young bullocks, a ram and seven lambs of the first year as a burnt offering, with the proper meat offerings and drink offerings, and a kid as a sin offering. (Numbers 28:11-15) As on the Sabbath, trade and handicraft work were stopped, (Amos 8:5) and the temple was opened for public worship. (Isaiah 66:23; Ezekiel 46:3) The trumpets were blown at the offering of the special sacrifices for the day, as on the solemn festivals.
(Numbers 10:10; Psalms 81:3) It was an occasion for state banquets. (1 Samuel 20:5-24) In later, if not in earlier, times fasting was intermitted at the new moons. Judith 8:6. The new moons are generally mentioned so as to show that they were regarded as a peculiar class of holy days, distinguished from the solemn feasts and the Sabbaths. (1 Chronicles 113:31; 2 Chronicles 2:4; 8:13; 31:3; Ezra 3:5; Nehemiah 10:33; Ezekiel 45:17) The seventh new moon of the religious year, being that of Tisri, commenced the civil year, and had a significance and rites of its own.
It was a day of holy convocation. The religious observance of the day of the new moon may plainly be regarded as the consecration of a natural division of time.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
NEW MOON. 1 Sam 20:5. See Moon, Feasts, Month.