Luke 13:24

Strive to enter in at the strait gate
What is meant by the strait gate, and by entering in at it, (See Gill on Matthew 7:13). To "strive", is to be diligent in the use of means; to search the Scriptures with care; to attend on the preaching of the word with constancy, neglecting no opportunity; to pray earnestly for spiritual light, knowledge, and grace; to contend with every enemy that opposes the salvation of the soul, as sin, Satan, and the world; to bear all reproaches and persecutions, and press through all difficulties, for the prize of the incorruptible crown: the metaphor seems to be taken from the striving, wrestling, and combat in the Olympic games, for a corruptible crown:

for many I say unto you, will seek to enter in, and shall not be
able:
either when it is too late, when the door is shut; or else before, very faintly, in a superficial manner, from a mere natural affection, from a principle of self-love, which leads every one to desire happiness; and by very indirect and improper methods, by their own civility, morality, and righteousness; by works of the law, moral, or ceremonial; or by a profession of religion, and an outward compliance with the ordinances of the Gospel, and not by Christ, and faith in him.