Is it permissible to ask God to see a miracle in a dream or while awake, or anything that strengthens faith, to increase certainty and avoid weakness?

Asking Allah for a sign is legitimate for prophets and for common people to increase their faith or to invite people to Islam, and there is no harm in that. However, one who is content with the proofs and follows the Sunnah (definition) is in a more perfect state than one who needs a miracle to firm his heart. The self-sufficiency of this Ummah from those who receive divine inspirations, those who are inspired, and those who have unveilings and dreams, is due to the perfection of its Prophet and his message. Thus, the rank of the truthful (Siddiqiyyah) is higher than the rank of receiving divine inspiration (Tahdith).