The author says: Since our previous treatise dealt with the duty to assume the service of G-d, I deemed proper to follow it with what is more necessary than all other things for one who serves G-d - placing one's trust in Him for all matters, the reason being the great benefits this yields both in religious and in secular matters.
בַּבִּטָּחוֹן עַל הָאֱלֹהִים יִתְבָּרַךְ לְבַדּוֹ.
אָמַר הַמְחַבֵּר מִפְּנֵי שֶׁקָּדַם מַאֲמָרֵנוּ בְּחִיּוּב קַבָּלַת עֲבוֹדַת הָאֱלֹהִים רָאִיתִי לְהָבִיא אַחֲרָיו מָה שֶׁהוּא צָרִיךְ יוֹתֵר מִכָּל הַדְּבָרִים לְעוֹבֵד הָאֱלֹהִים יִתְבָּרַךְ וְהוּא הַבִּטָּחוֹן עָלָיו בְּכָל דְּבָרָיו בַּעֲבוּר מָה שֶׁיֵּשׁ בּוֹ מִן הַתּוֹעָלִיּוֹת הַגְּדוֹלוֹת בְּעִנְיַן הַתּוֹרָה וּבְעִנְיַן הָעוֹלָם.
The author says: Since our previous treatise dealt with the duty to assume the service of G-d, I deemed proper to follow it with what is more necessary than all other things for one who serves G-d - placing one's trust in Him for all matters, the reason being the great benefits this yields both in religious and in secular matters.