Years ago, I bought a commentary by William MacDonald called Believer's Bible Commentary. I rarely use it anymore, because I have a few commentaries that are much better. The basic reason I rarely use it is because MacDonald is a Dispensationalist. Looking up Matt. 24:32, he does indeed believe it is referring to Israel.
However, without further information I would be very hesitant to associate them with Gnostics. I will say however that Matthew Henry's Commentary's Commentary seems to be supporting Israel as well.