Al-Haakim reports from the hadeeth of Aa`ishah (RA) that the Messenger of Allaah (sallallaahu ’alayhi wa sallam) said, "caution is of no avail against the decree but supplication benefits those things that have occurred and have not yet occurred. For indeed while the tribulation is descending the supplication meets it and they remain struggling with one another until the Day of Judgement."
[Reported by al-Haakim [1/492], at-Tabaraanee in 'al-Awsat' [no. 4615] and in 'ad-Du`aa' [no. 33], al-Bazzaar [3/29], al-Khateeb in his 'Taareekh' [8/453] and ibn al-Jawzee in 'al-Waahiyaat' [no. 1411]
Refer to: 'Saheeh al-Jaami' [2/1279 no. 7739].]
He also reports the hadeeth of ibn Umar from the Messenger of Allaah (sallallaahu ’alayhi wa sallam) that he said, "supplication brings about benefit to those things that have occurred and those things that have not yet occurred. So devote yourselves to supplication O servants of Allaah!"
[Mishkaat al-Masaabeeh [Eng. Trans. 1/472], at-Tirmidhee [no. 3548] and al-Haakim [1/493].
The hadeeth is hasan due to witnesses as declared so by as-Sakhaawee and al-Albaanee.
Refer to: 'Saheeh al-Jaami' [1/641 no. 3409] and 'Maqaasid al-Hasanah' of as-Sakhaawee [pg. 255 under no. 486].]