What is the ruling on the fasting of someone who prays only in Ramadan, or someone who fasts but does not pray?

Whoever is judged to be a disbeliever, their deeds are invalidated, based on the Almighty’s saying: (And had they associated others with Allah, then [all] that they used to do would have become worthless for them) and His saying: (And whoever disbelieves in faith—then has his work been made worthless, and he, in the Hereafter, will be among the losers). A group of scholars has held that one does not commit major disbelief if they affirm the obligation [of prayer], and that it is minor disbelief, and their act is more heinous than fornication and theft. Their fasting and Hajj are valid if performed lawfully, but their crime is the failure to maintain prayer. The correct view among scholars is that it constitutes major disbelief, so whoever fasts or performs Hajj but does not pray, has no fasting and no Hajj.