causes for stumbling: Or “stumbling blocks.” The original meaning of the Greek word skanʹda·lon is thought to have referred to a trap; some suggest that it was the stick in the trap to which bait was attached. By extension, the word came to refer to any impediment that would cause one to stumble or fall. In a figurative sense, it refers to an action or a circumstance that leads a person to follow an improper course, to stumble or fall morally, or to fall into sin. At Lu 17:2, the related verb skan·da·liʹzo, translated “stumble,” could also be rendered “become a snare to; cause to sin.”

seven times a day: This expression may have reminded Peter of the answer Jesus gave on an earlier occasion. Peter had asked Jesus how many times someone should forgive a brother. In that instance, Jesus replied: “Up to 77 times.” (See study note on Mt 18:22.) Neither of Jesus’ comments should be taken literally. “Seven times” here conveys the idea of an indefinite number of times. (Compare the expression “seven times a day” at Ps 119:164, which conveys the idea of repeatedly, constantly, always.) A Christian might sin against his brother seven times in a single day and repent seven times. If on being rebuked he is repentant, the sinner is to be forgiven every time. In those circumstances, forgiveness is to be extended indefinitely, or without limit.​—Lu 17:3.

the size of a mustard grain: Or “as small as a mustard seed.”​—See study note on Lu 13:19.

black mulberry tree: Or “sycamine tree.” This tree is mentioned only once in the Bible. The Greek word used was regularly applied to the mulberry tree, and the black mulberry (Morus nigra) is commonly cultivated in Israel. It is a sturdy tree that grows to a height of about 6 m (20 ft), with large heart-shaped leaves and dark-red or black fruit resembling the blackberry. This tree is known for having an extensive root system, thus requiring great effort to uproot.

put on an apron: The Greek word pe·ri·zonʹny·mai, rendered “put on an apron,” literally means “gird oneself about,” that is, to bind on an apron or to tighten the garments, often with a belt, in order to be prepared for service. In this context, the Greek word could also be rendered “get dressed and ready to serve.” The Greek word occurs at Lu 12:35, 37 and Eph 6:14.​—See study notes on Lu 12:35, 37.

good-for-nothing: Lit., “useless; worthless.” The point of Jesus’ illustration is not that the slaves, his disciples, are to consider themselves useless or worthless. According to the context, “good-for-nothing” conveys the idea that the slaves would view themselves modestly, not as deserving special credit or praise. Some scholars consider the term as it is used here to be hyperbole meaning “we are merely slaves deserving no special attention.”

While he was going to Jerusalem . . . passing between Samaria and Galilee: The final destination of this journey was Jerusalem, but Jesus first traveled N from the city of Ephraim through Samaria and Galilee (probably its southern part) to Perea. During this trip, while Jesus was entering a village either in Samaria or in Galilee, he was met by ten men who had leprosy. (Lu 17:12) This visit to Galilee was his last one prior to his death.​—Joh 11:54; see App. A7.

ten men with leprosy: In Bible times, lepers evidently congregated together or lived in groups, making it possible for them to help one another. (2Ki 7:3-5) God’s Law required that lepers live in isolation. A leper was also to warn others of his presence by calling out: “Unclean, unclean!” (Le 13:45, 46) In line with what the Law prescribed, the lepers stood at a distance from Jesus.​—See study note on Mt 8:2 and Glossary, “Leprosy; Leper.”

show yourselves to the priests: Jesus Christ, being under the Law while on earth, recognized the Aaronic priesthood as being in force, and he directed ones whom he cured of leprosy to go to the priest. (Mt 8:4; Mr 1:44) In accord with the Mosaic Law, a priest had to verify that a leper was healed. The cured leper had to travel to the temple and bring as an offering, or gift, two live clean birds, cedarwood, scarlet material, and hyssop.​—Le 14:2-32.

they were cleansed: This healing of the ten lepers by Jesus is reported by Luke alone.

with striking observableness: The Greek expression used here occurs only once in the Christian Greek Scriptures and is derived from a verb meaning “to watch closely; to observe.” According to some scholars, medical writers used this expression when they described watching the symptoms of disease. The way the word is used here seems to convey the idea that the Kingdom of God is not coming in a way that is obvious to all.

is in your midst: Or “is among you.” The pronoun “you” is plural in the original Greek and obviously refers to the Pharisees, to whom Jesus was speaking. (Lu 17:20; compare Mt 23:13.) Jesus was God’s royal representative, the one anointed by God for the kingship; hence, it could be said that “the Kingdom” was in their midst. Not only was he present in this capacity but he also had authority to perform works manifesting God’s kingly power and to prepare candidates for positions within his coming Kingdom.​—Lu 22:29-30.

just as lightning flashes: Jesus’ presence was to resemble lightning in that the evidence of his presence in Kingdom power would be clearly visible to all attentive onlookers.

so the Son of man will be in his day: Or possibly, “so the Son of man will be.” Some ancient manuscripts use the shorter reading, whereas other ancient manuscripts use this reading in the main text, as do many Bible translations.

the days of Noah: In the Bible, the term “day(s) of” is sometimes used with reference to the time period of a particular person. (Isa 1:1; Jer 1:2, 3; Lu 17:28) Here “the days of Noah” are compared to the days of the Son of man. In a similar statement recorded at Mt 24:37, the term “the presence of the Son of man” is used. Jesus does not limit the comparison just to the coming of the Flood as a final climax during Noah’s days, though he shows that his “days” or “presence” will see a similar climax. “The days of Noah” actually covered a period of years, so there is basis for believing that the foretold “days [or, “presence”] of the Son of man” would likewise cover a period of years, being climaxed by the destruction of those who do not seek deliverance.​—See study note on Mt 24:3.

ark: See study note on Mt 24:38.

Flood: Or “deluge; cataclysm.” The Greek word ka·ta·kly·smosʹ denotes a large flood with destructive force, and the Bible uses the word with reference to the Deluge of Noah’s day.​—Ge 6:17, Septuagint; Mt 24:38, 39; 2Pe 2:5.

on the housetop: The roofs of houses were flat and were used for many purposes, including storage (Jos 2:6), rest (2Sa 11:2), sleep (1Sa 9:26), and festivals for worship (Ne 8:16-18). That is why a parapet was required. (De 22:8) Generally, an external stairway or ladder allowed a householder to leave the rooftop without having to enter the house, which helps us understand how a person could heed Jesus’ warning and shows how urgent the situation would be.

life: Or “soul.”​—See Glossary, “Soul.”

be taken along: The Greek term rendered “taken along” is used in different contexts, often in a positive sense. For instance, at Mt 1:20, it is rendered “take . . . home”; at Mt 17:1, “took . . . along”; and at Joh 14:3, “receive . . . home.” In this context, it evidently refers to receiving a favorable standing with the “Lord” and being saved. (Lu 17:37) It may also correspond to Noah’s being taken into the ark on the day of the Flood and to Lot’s being taken by the hand and led out of Sodom. (Lu 17:26-29) To be abandoned would then mean to be judged worthy of destruction.

A few ancient manuscripts here include the words: “Two men will be in the field; one will be taken along, and the other will be abandoned.” However, these words do not appear in the earliest and most reliable manuscripts and are evidently not part of the original text of Luke. Similar words, though, can be found at Mt 24:40 as part of the inspired text. Some scholars are of the opinion that a copyist inserted the words from Matthew’s account into Luke’s account.​—See App. A3.