Ghafir: (67) It is He who created you...
{That you may reach your maturity}
This is linked to an omitted verb, the estimation of which is: "Then He sustains you so that you may reach your maturity."
{And likewise that you may be}
As for {and that you may reach a specified term}, its meaning is: "We do that so that you may reach a specified term," which is the time of death. It has also been said: the Day of Resurrection.
{As elders}
It is recited as shuyūkhan (with a kasra on the shin). It is also recited as shaykhan (in the singular), similar to His saying: {as an infant} (Al-Hajj: 5). The meaning is: "each one of you." Or, it is restricted to the singular because the purpose is to clarify the genus (the category).
{Before}
Meaning: before old age, or before these states occur, if one is born as a miscarriage.
{And that you may use reason}
Regarding what is in that [process] of lessons and proofs.
{It is He who gives life and causes death; and when He decrees a matter, He only says to it, "Be," and it is.}