A.T. Robertson Commentary Luke 13:24

"Strive to enter in by the narrow door: for many, I say unto you, shall seek to enter in, and shall not be able." — Luke 13:24 (ASV)

Strive (αγωνιζεσθε). Jesus makes short shrift of the question. He includes others (present middle plural of αγωνιζομα, common verb, our agonize). Originally it was to contend for a prize in the games. The kindred word αγωνια occurs of Christ's struggle in Gethsemane (Luke 22:44). The narrow gate appears also in Mt 7:13, only there it is an outside gate (πυλης) while here it is the entrance to the house, "the narrow door" (θυρας).