The Rabbis taught in a Baraisa* that seven things are concealed from people.

1. The day of a person's death. (repent all one's days)

2. The day of personal consolation (when one's anxiety or distress will be relieved, which was decreed for atonement)

3. The depth of judgement (most people judge erroneously, taking claims and testimonies at face value. Alternately, the judgement of the world to come is concealed in this world, for ten people might do the same sin and receive ten different judgements on High.)

4. What is in one's fellow's mind (thoughts or motivations)

5. What business activity will be profitable (so demand doesn't skyrocket or so people can earn a living)

6. When the Davidic monarchy will return

7. When the guilty monarchy will perish (current exile)

- Talmud - Tractate Pesachim - Page 54b