What is the ruling on a father refusing to marry off his 26-year-old daughter, who has received many marriage proposals, under the pretext of wanting her to stay with him for the rest of his life?

A woman's guardian does not have the right to prevent her from marrying a suitable match (righteous in faith and good in character). If he does so, he is considered to be preventing her marriage (عاضل), and his guardianship is transferred. Whether the guardianship transfers to a more distant guardian or to the ruler (Sultan) is a matter of scholarly disagreement. However, it transfers to the ruler if all guardians refuse. If there is no Muslim ruler available in the place, a just Muslim may marry her off with her permission.