A proper answer to this question would fill books. I will focus on the scripture you referred to.
There are promises and blessings associated with keeping the Sabbath. The Lord will:
1) cause (the Sabbath keeper) to ride upon the high places of the earth,
2) feed (the Sabbath keeper) with the heritage of Jacob.
These blessings relate to our relationship with the Lord and the Torah.
1) The "high places" in the Tanakh are nearly universally sites of idolatry and therefore the subject of great condemnation. But the Tanakh also mentions, the high places as the Lord's domain:
Job 25:2 KJV - Dominion and fear [are] with him, he maketh peace in his high places.
Amos 4:13 KJV - For, lo, he that formeth the mountains, and createth the wind, and declareth unto man what [is] his thought, that maketh the morning darkness, and treadeth upon the high places of the earth, The LORD, The God of hosts, [is] his name.
In Amos 4 (above) we have a connection between the Lord's creation, His giving man His word and the high places (which in my opinion is metaphorically, where we meet God).
Psalm 18:32-33 KJV - [It is] God that girdeth me with strength, and maketh my way perfect. He maketh my feet like hinds' [feet], and setteth me upon my high places.
Habakkuk 3:19 KJV - The LORD God [is] my strength, and he will make my feet like hinds' [feet], and he will make me to walk upon mine high places.
This is where His next blessing comes in!
Deuteronomy 33:3-4 Yea, he loved the people; all his saints [are] in thy hand: and they sat down at thy feet; [every one] shall receive of thy words. Moses commanded us a law, [even] the inheritance of the congregation of Jacob.
So, what is one of the many reasons the Sabbath is so important? Because it brings us into closer union with the Lord. As Isaiah 58:13-14 explains, in it:
we will not do our own ways -- but the Lord's ways
we will not seek our own pleasures - but the Lord's pleasures,
we will not speak our own words -- but the Lord's words
We will delight, [more and more] in the Lord
We will meet with Him in communion on His holy day
We will be given more insight from Torah (the heritage of Jacob)!
A lifetime of Sabbaths afford the non-scholar the opportunity to spend 16 uninterrupted, waking hours a week of time with the Lord and His word, leading to understanding and knowing the Lord and filling your life with the delight of His word.
Thus saith the LORD, Let not the wise [man] glory in his wisdom, neither let the mighty [man] glory in his might, let not the rich [man] glory in his riches: But let him that glorieth glory in this, that he understandeth and knoweth me, that I [am] the LORD which exercise lovingkindness, judgment, and righteousness, in the earth: for in these [things] I delight, saith the LORD. - Jeremiah 9:23-24 KJV
But his delight [is] in the law of the LORD; and in his law doth he meditate day and night. - Psalm 1:2 KJV
I delight to do thy will, O my God: yea, thy law [is] within my heart. - Psalm 40:8
In the multitude of my thoughts within me thy comforts delight my soul. - Psalm 94:19
Psalm 119:35, 77, 174 KJV
Make me to go in the path of thy commandments; for therein do I delight.
Let thy tender mercies come unto me, that I may live: for thy law [is] my delight.
I have longed for thy salvation, O LORD; and thy law [is] my delight. -
And I will give them an heart to know me, that I [am] the LORD: and they shall be my people, and I will be their God: for they shall return unto me with their whole heart. Jeremiah 24:7