Isaiah 56:7 (KJV) Even them will I bring to my holy mountain, and make them joyful in my house of prayer: their burnt offerings and their sacrifices shall be accepted upon mine altar; for mine house shall be called a house of prayer for all people.
In Mark 11:15, Jesus cleared the temple of the money changers and thieves. It was figurative of how He had to prepare us to be a dwelling place for the Holy Spirit. That temple was the body of the believer, His new home(1). This was necessary for us to be an acceptable place for Him to dwell.
After clearing the temple, Jesus referenced the verse at the top (Mk. 11:17). Since we are His temple, we are a house of prayer for all people. That means people of all sorts and races.
The task of a born-again believer is to bring the power of God into a world that desperately needs it. We can do this by releasing fruit of the Spirit, speaking God's Word, and through prayer. Our verse at the top says, "I [God] will make them joyful in my house." An amazing benefit of prayer is the Joy it can produce.
I continually pray and bless people. When I bless my food, I also bless the hands that served it and prepared it, even in restaurants. If I drive past a car accident, I pray God brings good out of it for the people involved. If someone seems to get my attention---I pray for them---even if I do not know anything about them, I bless them. I continually bless people and pray for them, and I continually walk in joy.
I pray simple prayers, sometimes under my breath, or even in my thoughts. God hears it, and He is released into their lives, fulfilling my requests.
Praying for others can also be a powerful antidepressant. Psalm 126:5 says, "Those who sow in tears shall reap in joy." When we pray for others, we sow into their lives. When we feel sad or depressed, God has provided a way out---pray for others.
Of course, we do not have to wait until we are depressed to take advantage of this remarkable gift. Pray simple prayers for all kinds of people and walk continually in the joy of the Lord.
(1) 1 Corinthians 6:19 (NKJV), "Or do you not know that your body is the temple of the Holy Spirit who is in you, whom you have from God, and you are not your own?"