{Which for a while believe} (hoi pros kairon pisteuousin).
Ostensibly they are sincere and have made a real start in the
life of faith. {They fall away} (aphistantai). Present middle
indicative. They stand off, lose interest, stop coming to church,
drop out of sight. It is positively amazing the number of new
church members who "stumble" as  Mr 4:17  has it
(skandalizontai), do not like the pastor, take offence at
something said or done by somebody, object to the appeals for
money, feel slighted. The "season of trial" becomes a "season of
temptation" (en kair(9369) peirasmou) for these superficial,
emotional people who have to be periodically rounded up if kept
within the fold.