Jamieson, Fausset and Brown on Philippians 3:18

18. many walk--in such a manner. Follow not evildoers, because they are "many" (Ex 23:2). Their numbers are rather a presumption against their being Christ's "little flock" (Lu 12:32).

often--There is need of constant warning.

weeping--(Ro 9:2). A hard tone in speaking of the inconsistencies of professors is the very opposite of Paul's spirit, and David's (Psa 119:136), and Jeremiah's (Jr 13:17). The Lord and His apostles, at the same time, speak more strongly against empty professors (as the Pharisees), than against open scoffers.

enemies of the cross of Christ--in their practice, not in doctrine (Ga 6:14; He 6:6; 10:29).