Because God saved us...we are to do good

“It is a faithful saying.” 2 Timothy 2:11
Paul has four of these “faithful sayings.” The first occurs in 1 Timothy 1:15, “This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners.” The next is in 1 Timothy 4:6, “Godliness is profitable unto all things, having the promise of the life that now is, and of that which is to come. This is a faithful saying, and worthy of all acceptation.” The third is in 2 Timothy 2:12, “It is a faithful saying-If we suffer with him we shall also reign with him”; and the fourth is in Titus 3:8, “This is a faithful saying, that they which have believed in God might be careful to maintain good works.” We may trace a connection between these faithful sayings. The first one lays the foundation of our eternal salvation in the free grace of God, as shown to us in the mission of the great Redeemer. The next affirms the double blessedness which we obtain through this salvation-the blessings of the upper and nether springs-of time and of eternity. The third shows one of the duties to which the chosen people are called; we are ordained to suffer for Christ with the promise that “if we suffer, we shall also reign with him.” The last sets forth the active form of Christian service, bidding us diligently to maintain good works. Treasure up these faithful sayings. Let them be the guides of our life, our comfort, and our instruction. Let these four faithful sayings be written on the four corners of my house. (From Spurgeon's Morning and Evening Devotions)

Titus 3:3-8(NASB)
For we also once were foolish ourselves, disobedient, deceived, enslaved to various lusts and pleasures, spending our life in malice and envy, hateful, hating one another. But when the kindness of God our Savior and His love for mankind appeared, He saved us, not on the basis of deeds which we have done in righteousness, but according to His mercy, by the washing of regeneration and renewing by the Holy Spirit, whom He poured out upon us richly through Jesus Christ our Savior, so that being justified by His grace we would be made heirs according to the hope of eternal life. This is a trustworthy statement; and concerning these things I want you to speak confidently, so that those who have believed God will be careful to engage in good deeds. These things are good and profitable for men.

Be careful to engage in good deeds.