19.Not an iota of没有一点点，丝毫也不

iota是希腊字母表中第９个字母"Ｉ"的名称。not an iota of 出自《新约。马太福音》第５章："律法的一点一画都不能废去，都要成全。"因为iota是希腊字母表中最小的一个字母，它有时可以写作一短横置于其他字母之上；遗漏这一点点对发音并无什么影响，只按规则不能减少而已。《福音书》所说的律法，系指"摩西律"，意即无论何人都不允许随便废去这戒律哪怕是最小的一条，甚至其中的一个字母，一个小小短横也不得更动或遗漏。

由此，在语言中遗留下来这个成语，转义表示not a bit of ;not one jot or little; not at all等意思。iota在这里，相当于汉语"小不点儿"的意思。

Eg: Science deals with things in a practical way. Science means honest, solid knowledge, allowing not an iota of falsehood, and it involves Herculean efforts and grueling toil.

There is not an iota of truth in the story.

20.The Salt of the Earth社会中坚；民族精华；优秀份子

The Salt of the Earth这个成语，字面意思"世上的盐"

盐是饮食中不可缺少的调味品，人体若缺盐，健康就会受到影响，出现种种疾病。盐还有杀菌、解毒、消炎、除污等多种功用，它既是"百药之王"，又是工业之母，确是值得珍视的东西。在许多民族的习俗汇总，盐被当作敬客的高贵礼品。

The Salt of the Earth一词出自《圣经》，据《新约。马太福音》（Matthew）第５长记载：耶稣对他的门徒说:"Ye are the salt of the earth: but if the salt have lost his savor, wherewith shall it be salted? " 在这里，salt用于转义，表示flavor；of the earth即of the world。这是耶稣登山垂训论"福"，所讲福音结尾的话，他把门徒比做"世上的盐"，这是极高的称赞。这句话在后世不断引用变成了一个典故性成语，转义为the most valuable members of society; the finest type of humanity; a person or a group of people having the best character 之意

eg: He does a lot of good jobs and is considered to be the salt of the world.

You all are the salt of the earth. Our hope is placed on you

21.Cast pearls before swine对牛弹琴；白费好意

To Cast pearls before swine的意思是"珍珠投在猪猡前面"。swine是个旧词，书面词，即今为pigs,不过swine单复同行，本句为复数。

这个成语源自《新约。马太福音》第7章："Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you".由于to cast pearls before swine,比喻确切，在后世不断引用中而成为一个国际性成语，常用来表示to offer sth valuable or beautiful to those who can't appreciate it; to give what is precious to those who are unable to understand its value等意思，含有轻蔑嘲笑色彩。按其字面意义，这个成语与汉语成语"明珠按投"相似，但是寓意不同，基本上不对应；按一比喻意义，它相当于"对牛弹琴"，"向驴说经""一番好意给狗吃""狗咬吕洞宾，不识好人心"等。

She read them Shakespeare, but it was casting pearls before swine

I won't waste good advice on John any more because he never listens to it.I won't cast pearls before swine.

……and when I let the upper floor to Cap'en Cuttle, oh I do a thankless thing, and cast pearls before swine

22.a wolf in sheep's clothing批着羊皮的狼；貌善心恶的人

耶稣在加利利一带传道布教，收了很多信徒。有一天，他对门徒说:"Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves"

eg: Mrs. Martin trusted the lawyer until she realized that he was a wolf in sheep's clothing

One who teaches morality and practises immorality is a wolf in lamb's skin

23.separate the sheep from the goats区别好坏，分清良莠

《新约。马太福音》记述："And before him shall be gathered all nations: and he shall separate them one from another, as a shepherd divides  his sheep from the goats"

由于《圣经》的影响，sheep和goat在英语中的形象截然不同，前者比喻好人，后者比喻坏人。英语中有关goat的成语，大多贬义。如：to play the goat=play the fool（瞎胡闹）；to get sb's goat（触动肝火） ；等等。《圣经》说牧羊人要分辨绵羊和山羊，"把绵羊安置右边，山羊左边"。据说野山羊常混进羊群里，引诱绵羊，故牧养人必须把它们区分开来，以免混淆。

由此，人们用to separate the sheep from the goats这个成语，来比喻to separate the good from the wicked; to divide good or useful people from bad or useless

eg: We'll go through the list of members, and separate the sheep from the goats

Have faith in me, please. I can separate the sheep from the goats