Albert Barnes Commentary 2 Timothy 2:12

"if we endure, we shall also reign with him: if we shall deny him, he also will deny us:" — 2 Timothy 2:12 (ASV)

If we suffer, we shall also reign with him. The meaning is, that the members will be treated as the Head is. We become united with him by faith; and, if we share his treatment on earth we shall share his triumphs in heaven. (See Barnes on Romans 8:17).

If we deny him, he also will deny us. (See Barnes on Matthew 10:32 and Matthew 10:33).