Answer
(Fatwa: 790/623/D=1431)
The dream is quite clear that your father is in good condition in akhirah and he is worried for religiousness of his children and their punctuality of salah. Since every week the deeds of living people are presented on dead ones, hence it is possible that he found your laziness in salah and you were warned by unseen indication. So you should be regular in offering salah with jamah, and recite the following dua after salah as well:
رب ارحمها كما ربيانى صغيراً
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband