* **the required number of days** - This could be translated as "the number of days that God required."
* **for their purification** - "for them to become ceremonially clean" or "for God to consider them to be clean again"
* **to present him to the Lord** - "to bring him to the Lord" or "to bring him into the Lord's presence." This was a ceremony acknowledging God's claim on the firstborn children who were male.
* **male that opens the womb** - This is an idiom for "firstborn offspring that is a male." The law was about the firstborn offspring of both people and domestic animals, but in this context it could be translated as "firstborn son." (See: [[en:ta:vol1:translate:figs_idiom]])