Oath

Exodus 20:7
"You shall not misuse the name of the LORD your God, for the LORD will not hold anyone guiltless who misuses his name." (This establishes the sanctity of God’s name, which is often invoked in oaths.)

Numbers 30:2
"When a man makes a vow to the LORD or takes an oath to obligate himself by a pledge, he must do according to all he said he would do."

Deuteronomy 10:20
"Fear the LORD your God and serve him. Hold fast to him and take your oaths in his name."

Psalm 76:11
"Make vows to the LORD your God and fulfill them; let all the neighboring lands bring gifts to the One to be feared."

Ecclesiastes 5:4-5
"When you make a vow to God, do not delay to fulfill it. He has no pleasure in fools; fulfill your vow. It is better not to vow than to make a vow and not fulfill it."

Obey

Deuteronomy 5:33
"Walk in obedience to all that the LORD your God has commanded you, so that you may live and prosper and prolong your days in the land that you will possess."

1 Samuel 15:22
"But Samuel replied: 'Does the LORD delight in burnt offerings and sacrifices as much as in obeying the LORD? To obey is better than sacrifice, and to heed is better than the fat of rams.'"

Proverbs 3:1-2
"My son, do not forget my teaching, but keep my commands in your heart, for they will prolong your life many years and bring you peace and prosperity."

Isaiah 1:19
"If you are willing and obedient, you will eat the good things of the land."