Does the reward and merit of a righteous deed, done sincerely for the sake of Allah, go away if Allah Almighty is asked for a worldly matter through it?

It is permissible to seek intercession through good deeds to bring benefits and repel harms. This intercession does not diminish the reward of the deed through which intercession is sought, whether the need is worldly or related to the Hereafter. The companions in the cave sought intercession through their best deeds for worldly needs. Seeking intercession through good deeds is from the "means" (al-wasilah) that Allah commanded in His saying: "O you who have believed, fear Allah and seek means [of nearness] to Him."