This is not the only place in Paul’s letters where he emphasises the relevance of the Old Testament for the New Testament church. See, for example, Romans 15:4 and 2 Timothy 3:16–17.
Christians live in the end of the ages,
that is, in the last phase of God’s salvation plan. This phase of history was introduced with Christ’s first coming and his death on the cross (Hebrews 9:26). It will end with Christ’s second coming (Matthew 13:39–40, Matthew 13:49; Matthew 28:20).
11 Now these things happened to them as an example, but they were written down for our instruction, on whom the end of the ages has come.