Luke 1:14
Luke 1:1414He will be a joy and delight to you, and many will rejoice at his birth,
receives little JW commentary. Where it does appear, it is read as a prophecy that John the Baptist's life would bring joy to many people, with no implication for the question of birthday celebration. The Watchtower's birthday ban, drawn from Genesis 40 (Pharaoh) and Matthew 14 (Herod) and amplified by pagan-origin claims, treats as background colour rather than as counter-evidence.
Pair with ("cursed be the day I was born") and ("Job opened his mouth and cursed the day of his birth") to dismantle the Watchtower's claim that the Bible is silent or negative about birth-days. Jeremiah and Job both curse a day they presuppose was normally blessed — you cannot curse the ordinary blessedness of a day that was not customarily blessed. And here, the angel Gabriel prophesies that "many will rejoice over [John's] birth." If Scripture rejoiced at the birth of one prophet and treated the day of birth as normally blessed in the case of others, the Watchtower cannot use Pharaoh and Herod (the only two birthday celebrations the rs book identifies) to ground a universal prohibition. The two-pagan-tyrants sample size collapses against the broader scriptural picture.