Artscroll Hebrew Siddurim - and 1 2 among others have at the end of Hallel to say the following Posuk.
וְאַבְרָהָם זָקֵן בָּא בַּיָּמִים וַה' בֵּרַךְ אֶת-אַבְרָהָם בַּכֹּל
Artscroll says it is a Segula for Arichas Yomim. Artscroll does not bring a source.
What is the source for saying this Posuk at the end of Hallel? Why specifically on Rosh Chodesh?
