5) There are a number of answers:
i) The Gemara in Bava Metzia (110b)
Brought down l’halachah in Choshen Mishpot 339 teaches, that if someone asks his friend to hire workers for him then neither of them violate בל תלין. The one who arranged the workers doesn’t transgress as they are not his workers, and the employer doesn’t transgress as he never hired them. We see that if one uses an agent then he doesn’t violate בל תלין. If so, since the Torah was given to us via Moshe Rabbeinu and not directly from Hashem, there is no בל תלין (Chanukas HaTorah, Yisro; Yismach Moshe, Matos; and Chida in Ruach Chaim, Derush 2, and Nachal Kedumim, Vo’eschanan)
The Yismach Moshe adds: The Medrash says: “Yisroel are only sustained through the merit of emunah”. It’s clear from the Gemara (Makkos 24a and Horiyas 8a) that the first two of the Aseres HaDibros, אנכי and לא יהיה לך, were given by Hashem Himself. Based on the above, we can explain: Since the first two commandments which are about emunah were given directly from Hashem, He is obligated to pay up immediately, and for these commandments there is reward in this world. This is what it means we are sustained through emunah, we are sustained through the reward we get in this world for emunah.
With this we can understand the pasuk, צדיק באמונתו יחיה . Through the mitzvah of emunah a tzadik lives, i.e. he gets reward in this world.
ii) The Halachah of Returning an Item
The halachah is (339:6) that if one gives an item to a worker to fix and he fixes it, as long as it hasn’t yet been returned to the owner there is no בל תלין, even if the owner has been notified that he itme is finished. However, once it is returned to the owner, if he doesn’t pay that day then he violates בל תלין. Based on this, as long as one is alive in this world, he hasn’t yet returned his utensil (his neshomah) to the owner, therefore, Hashem doesn’t violate בל תלין. However, once one dies and he returns the utensil to the owner (i.e. his neshoma), then there is בל תלין, and by that time Hashem does pay up (Kesonas Pasim, cited in Pardes Yosef, Vo’era pg. 45).
iii) Chazal's Drasha on the Pasuk
Chazal darshen the pasuk, מה יתרון לאדם בכל עמלו שיעמל תחת השמש, to mean, that all the mitzvos and ma’asim tovim that one does doesn’t come to close to the benefit one gets when Hashem makes the sun, shine. According to this Hashem doesn’t need to pay, as he has already given us more than we give Him, therefore there is no baal tolin. (Chida)
iv) Serving Hashem Like a Slave
We are obligated to serve Hashem like a slave, and if Hashem who is our King decides to pay us, it’s more like a bonus than it is payment. Since it’s not considered payment, there is no issue of ba’al tolin.
