In looking at how to approach the Sermon on the Mount, I’ve wrestled with how to translate the word translated perfect in Matthew 5:48 and while my suspicion is that perfect is not a good translation for the Greek work telos, I wanted to look more broadly at how the scriptures dealt with the idea of being perfect, perfection or blameless.
Perfect, Perfection and Blamelessness in the Hebrew Scriptures
There are two primary words in Hebrew that end up translated perfect, perfection and blameless and they are related two each other. Hebrew words begin as a verbal form and so the verb root is :תָּם
(Tam) which in its Qal form means to complete, finish, fulfill, to be finished, come to an end and in its Hitp’ael form means finish, complete, perfect, cease doing a thing, complete or shut up.This verb also has a noun form (Tim) and the more common for our current examination adjectival form Tamim. There are a few other Hebrew terms which get translated perfect or blameless (for example Daniel 6:22 translates a term that normally is translated purity (zaku) for blameless and Lamentations and Ezekiel use the word kelil for a poetic reflection of perfection in terms of beauty).
In the Hebrew Scriptures these translations rarely talk about moralistic perfection which is often implied to an English reader of the words perfect, perfection, and blameless and below I am listing my categories of what these translations are referring to:
Righteousness/Justice is an important concept in Hebrew thought, but I think it is easy for us to assign a modern interpretation on Justice or the Law which doesn’t coincide with a Hebrew way of understanding the gift implied in these terms. Often when Tam or Tamim is translated blameless it is referring to the concept of a person being innocent or righteous. In both Hebrew and Greek justice and righteousness are rooted in the same term (tszadik in Hebrew, dikaisoune in Greek) and while there is a sense where righteousness is linked to keeping the commands and ordinances of the law, it more broadly encompasses living in a right relationship with God and one’s neighbors. Tamim or Tam can be translated in parallel with righteousness, for example in Genesis 6:9 Tamim is translated blameless in parallel with righteousness and refers to Noah being innocent unlike his generation: “Noah was a righteous man, blameless in his generation” (see also Genesis 17:1 in relation to God calling Abram to be innocent (blameless)). This is also the primary way the book of Job uses the Tam and Tamim family of words, for example: There is no one like him, a blameless and upright man (Job 2:3, see also Job 1:1, 8; 8:20; 9:20, 21,22; 12:4; 22:4). Being blameless is parallel to being upright or righteous but it is not used in the sense of legalistically keeping every possible interpretation of the law, instead it is often used more generally to speak of a person’s character being in accordance with God’s intent for life in the community of faith.
Sacrificial Acceptability or Completion in Dedication to God
Another usage of Tamim or Tam when translated perfect is related to a cultic usage where a sacrifice or item is acceptable for use in sacrifice or the worship of God. Leviticus 22:21 is an example of this usage for a sacrifice, “When anyone offers a sacrifice of well-being to the LORD, in fulfillment of a vow or as a freewill offering, from the herd or from the flock, to be acceptable it must be perfect; there shall be no blemish in it.” This also is used when the temple is dedicated in 1 Kings to talk about the completion of the space in preparation for worship, “Next he overlaid the whole house with gold, in order that the whole house might be perfect; even the whole altar that belonged to the inner sanctuary he overlaid with gold”(1 Kings 6:22). Tamim and Tamm are used to reflect completeness or wholeness, which is the sense of perfect reflected by the translation. A sacrifice must be without injury, illness or blemish or the sanctuary was completely overlaid with gold without missing any area.
Completeness/Righteousness in relation to God
This use of Tamim (always the adjective in this usage) occurs in songs and poetry when talking about God as being complete or whole in relation to God being upright. Deuteronomy 32:4 is the first usage of this type in the song of Moses, “This God—his way is perfect; the promise of the LORD proves true; he is a shield for all who take refuge in him” (also used in this manner in David’s song of Thanksgiving in 2 Samuel 22: 31 and in Psalm 18:30)
Completeness in relation to knowledge or content
In the book of Job, the final human voice to speak prior to God’s answer is Elihu who attempts, like the other friends of Job, to convince Job that he must be unrighteous to merit the suffering he is undergoing. In his boasts he claims to have perfect knowledge (or to be in the presence of God who has perfect knowledge) in the sense of knowing everything correctly or completely. (Job 36:4, 37:16) Psalm 19:7 can also refer to the law as being complete in a similar (but non-ironic) manner, “The law of the LORD is perfect, reviving the soul; the decrees of the LORD are sure, making wise the simple”
Poetic Use in Relation to Beauty or Splendor
Perfect or perfection is often used in compliments to poetically state that a person, city or event was attractive, beautiful or wonderful. This is one of the most common usages of Tamim and Tam in Psalms, Song of Solomon, Lamentations, and Ezekiel (which also uses the Hebrew word kelil) and can be used for a woman, a king, the law or even a city like Jerusalem or Tyre. For example, Song of Solomon can refer to a woman, “Open to me, my sister, my love, my dove, my perfect one; for my head is wet with dew, my locks with the drops of night” (Song of Solomon 5:2, see also 6:9). The king of Tyre is described as a signet of perfection and perfect in beauty (Ezekiel 28:12), the law is perfect in terms of admiration(Psalm 119:96) as are Jerusalem (Psalm 50:2, Lamentations 2:15, Ezekiel 16:14) and Tyre (Ezekiel 27: 3-4, 11).
Translated Perfect or Blameless in the New Testament (other than Telos/Teleo)
There are a couple words that get translated perfect or blameless in the New Testament: amemptos is commonly used in Pauline literature and is translated blameless and echoes the sense of innocence/righteousness discussed above for Tam and Tamim in Hebrew. Other terms that get translated as either perfect or blameless (other than telios which will be the focus of the next section) include: amomos (unblemished in terms of sacrifice, blameless in moral terms, Revelation 14: 5), anegkletos (blameless, irreproachable, 1 Timothy 3:10, Titus 1: 6, 7) akakos (innocent, guileless, Hebrews 7:26) holoklepia (wholeness, completeness, soundness-wholeness of health, Acts 3: 16); kataptisis (being made complete, complete, 2 Corinthians 13:9); pas (all, full, great) and plerow (make full, fill, fulfill, bring to completion, Revelation 3:2). Each of these translations capture one of the senses listed for tam and tamim above but since the focus of this is on the translation of the term telos in Matthew’s gospel, we will now turn our attention to this word.
Translating Telos/Teleo in Matthew and the New Testament.
Teleo (verb) and telos (noun) and their derivatives, especially the adjectival form, in Greek are the most common terms translated perfect by the NRSV. The book of Hebrews frequently uses this term in the sense of completeness or sacrificial acceptability. James and 1 John use the term in the sense of highest in terms of comparison (perfect love, perfect law, perfect gift, etc.).Paul uses telos and teleo derivatives three times to indicate completeness which get translated perfect in the NRSV (Romans 12: 2; 2 Corinthians 7:1; 12:9)
Teleios, the adjectival derivative of telos, occurs three times in the gospels, all in the Gospel of Matthew: Matthew 5:48 (twice) and Matthew 19:21 and the NRSV translates each time as perfect:
Matthew 5: 48 Be perfect, therefore, as your heavenly Father is perfect
Matthew 19: 21 Jesus said to him, “If you wish to be perfect, go, sell your possessions, and give the money to the poor, and you will have treasure in heaven; then come, follow me.
The telos family of words are words of ending, completion and reaching a goal, they don’t carry the connotation of moralistic perfection that placing the word perfect in English does. Apparently, this translation goes back to the Latin Vulgate which translates teleios with the latin perfecti and perfectus and translations tend to value consistency with previous translations when possible. However, the lingering impact of perfect on the history of translation of this passage has caused people to hear the Sermon on the Mount as an unattainable pillar of perfection that is unable for human beings to attain. I would argue for a more literal translation in both Matthew 5:48 and 19:21 of complete instead of perfect for reasons I will argue in the introduction to the Sermon on the Mount and in the comments on Matthew 5: 48.
 Hebrew verbs have various forms (Qal, Nif’al, Pi’el, Pu’al, Hitpa’el, Hif’il and Hof’al) the Qal is the simple active form where the Hitpa’el is the reflexive form. The form of the verb can significantly change a meaning, but in the case of Tam they are very similar with minor shades of difference.
 Philippians 1:10; 2: 15; 3:6; Colossians 1: 22; 1 Thessalonians 2: 10; 3: 13; 5: 23
 Hebrews 2:10; 5:9; 7:19; 9:9, 11; 10:1; 11:40; 12:23; James 1:17, 25; 3:2; 1 John 4:8
 I 1 Corinthians 1:8 the NRSV translates telos in its normal meaning as end