Like the Bible's teaching regarding the wife's submission to her husband (see Bookmark for page 84 above), Scripture's teaching (and hence Lewis's comment here) on homosexuality has fallen out of favor in many cultures today. Nonetheless, Bible passages that prohibit homosexuality include the following (quoted from the English Standard Version).
Leviticus 20:13: "If a man lies with a male as with a woman, both of them have committed an abomination; they shall surely be put to death; their blood is upon them."
1 Corinthians 6:9-10: "Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God."
1 Timothy 1:8-11: "Now we know that the law is good, if one uses it lawfully, understanding this, that the law is not laid down for the just but for the lawless and disobedient, for the ungodly and sinners, for the unholy and profane, for those who strike their fathers and mothers, for murderers, the sexually immoral, men who practice homosexuality, enslavers, liars, perjurers, and whatever else is contrary to sound doctrine, in accordance with the gospel of the glory of the blessed God with which I have been entrusted."
See also Romans 1:18-32.