Laylat al-Qadr may be seen with the eye, for the one whom Allaah helps to see it. That is by seeing its signs. The Sahaabah (may Allaah be pleased with them) used to recognize it by its signs. But not seeing them does not means that one will not gain its reward, if one spends that night in prayer out of faith and the hope of reward. The Muslim should strive to seek it in the last ten nights of Ramadaan, as enjoined by the Prophet (peace and blessings of Allaah be upon him), hoping to earn reward. If it so happens that a person spends this night in prayer out of faith and seeking reward, then he will gain its reward, even if he does not know that that was Laylat al-Qadr. The Prophet (peace and blessings of Allaah be upon him) said: Whoever spends the night of Laylat al-Qadr in prayer out of faith and seeking reward, all his previous sins will be forgiven. According to another report: Whoever spends that night in prayer, seeking Laylat al-Qadr, then he catches it, his previous and future sins will be forgiven.
And a sound report from the Prophet (peace and blessings of Allaah be upon him) indicates that the sign of Laylat al-Qadr is that the sun rises on the following morning with no visible rays. Ubayy ibn Ka'b used to swear that it was the night of the twenty-seventh, citing this sign as evidence. The more correct view is that it moves through all the last ten nights, but it is most likely to be one of the odd-numbered nights, and the night of the twenty-seventh is the most likely among the odd-numbered nights. Whoever strives in worship during all of the last ten nights, praying, reading Qur'aan, making du'aa' and other kinds of good deeds will undoubtedly catch up with Laylat al-Qadr and attain what Allaah has promised to those who do that out of faith and seeking reward.
And Allaah is the Source of strength, May Allaah bless our Prophet Muhammad and his family and companions.
Reproduced from Islam QA