Adam Clarke on Luke 2:29

Lord, now lettest thou thy servant depart in peace - Now thou dismissest, απολυεις, loosest him from life; having lived long enough to have the grand end of life accomplished.

According to thy word - It was promised to him, that he should not die till he had seen the Lord's anointed, Luk 2:26; and now, having seen him, he expects to be immediately dismissed in peace into the eternal world; having a full assurance and enjoyment of the salvation of God. Though Simeon means his death, yet the thing itself is not mentioned; for death has not only lost its sting, but its name also, to those who have, even by faith, seen the Lord's anointed.