Skandapurana 5.59.21

5.59.21

māghamāsasya saptamyāṃ sūryavāreṇa yo naraḥ ..
pūjayedbhāskaraṃ tatra sa yāti paramāṃ gatim .. 21 ..

Whatever person worships the Sun there on the seventh day of the month of Māgha, / falling on a Sunday, goes to the highest state;