When does Allah breathe the soul into the human fetus, and what are the stages of fetal development?

Abdullah ibn Mas'ud (may Allah be pleased with him) narrated that the creation of man passes through three stages, each lasting forty days: a drop of fluid (nutfah), then a clinging clot (alaqah), then a chewed lump of flesh (mudghah). After that, the soul is breathed into him, and his lifespan, deeds, sustenance, and whether he will be wretched or happy are decreed. Scholars have agreed that the ensoulment occurs after four months, i.e., one hundred and twenty days. Al-Hafiz Ibn Hajar added that the Holy Qur’an mentioned two additional stages: the stage of bones, and then the clothing of the bones with flesh.