Tafseer Ibn Kathir of AL 'ANKABUUT [64]

64. And this life of the world is only an amusement and a play! Verily, the home of the Hereafter -- that is the life indeed, if they but knew. 65. And when they embark on a ship, they invoke Allah, making their faith pure for Him only, but when He brings them safely to land, behold, they give a share of their worship to others. 66. So that they become ingrate for that which We have given them, and that they take their enjoyment, but they will come to know.  

(Verily, the home of the Hereafter -- that is the life indeed,) means, the true everlasting life that will never end, but will continue forever and ever.

(if they but knew.) means, they would prefer that which will last over that which will pass away. Then Allah says that at times of calamity, the idolators call upon Him alone, with no partner or associate, so why do they not do that all the time

(And when they embark on a ship, they invoke Allah, making their faith pure for Him only,) This is like the Ayah,

(And when harm touches you upon the sea, those that you call upon vanish from you except Him (Allah Alone). But when He brings you safely to land, you turn away) (17:67). Allah says here:

(but when He brings them safely to land, behold, they give a share of their worship to others.) Muhammad bin Ishaq reported from `Ikrimah bin Abi Jahl that when the Messenger of Allah conquered Makkah, he (`Ikrimah) ran away, fleeing from him. When he was on the sea, headed for Ethiopia, the ship started to rock and the crew said: ”O people, pray sincerely to your Lord alone, for no one can save us from this except Him.'' `Ikrimah said: ”By Allah, if there is none who can save us on the sea except Him, then there is none who can save us on land except Him either, O Allah, I vow to You that if I come out of this, I will go and put my hand in the hand of Muhammad and I will find him kind and merciful.'' And this is what indeed did happen.

(So that they become ingrate for that which We have given them, and that they take their enjoyment,)