From Ibn `Abbas said, when verse comes down ,
"And warn your relatives to the nearest "(Surah Ash-Syu'araa :
214), and those who are sincere of your tribes, Rasulullah SAW
straight out to the Safa hill, then shouted, "Yes Shabaahaah!" (call
to gather in the morning). They wonder, "Who is this screaming?" They
replied, 'Muhammad.' They were soon gathered to him. Rasulullah SAW
called (again), "O Bani so and so, O Bani so and so, O Bani Abdi
Manaaf, O Children of Abdul Muttalib!" Then gathered the people (of
the tribes mentioned earlier) to him. " Rasulullah SAW said (after
they get together) again, "What do you think, if I were to tell you
that a horse will come out at the top of this hill, what would you
justify me?" They replied, "We have not seen you lie." Rasulullah SAW
then said, "Know that I am the warner among a painful punishment." Abu
Lahab answered immediately, "Tabban laka (you ruined)! Is it just for
this you collect we?! "then he got up and left, then came down this
letter," perish the hands of Abu Lahab "and indeed he actually perish.
(Bukhari, no. 4589 and Muslim, no. 307, and the wording of this hadith belongs to Muslims )
About the 'monday' ..
Saheeh Bukhari juz VI page 125, Dar al-Fikr printed in 1401 H - 1981 M / 1/591, Maktabah syamilah
The story is that Abu Lahab so happy with the birth of the Rasulullah SAW (which turned out to be his mortal enemy) and jubilant at the time, until on that Monday Abu Lahab freed a slave named Tsuwaibah .. maybe that's why ..