In Romans chapters 1 and 2 we are told that there are two things which conclusively testify to mankind about the true and living God and leave mankind without an excuse:
CREATION, that is the visible things that are in the world and clearly seen, testifies to the existence of the Creator God (Romans 1:20).
CONSCIENCE, that is, the instinctive way in which each man knows that there is a law of right and wrong written in his heart, even though he may not have read God’s word (Romans 2:14 – 15).
But to the man who has heard the gospel, the good news about God’s love for man through Jesus Christ, the best way to know God is to ‘Taste and see.’ ‘Taste and see that the Lord is good; for blessed is the man that trusts in Him’ (Psalm 34:8). Simply take a step of faith, trusting that God is real, and ask God (through prayer) to reveal Himself to you. Ask Him to open the eyes of your understanding so that you may be enlightened concerning the truth (Ephesians 1:18).
Then read the Gospel of John and God will reveal His love to you from His Word. This miracle of His grace will help you to know God.
Islâm teaches that you will know there is a God through His creation. (Surah 3 Ali ‘Imran ayat 190-191 and Surah 28 Al Qasas ayat 71 -72). Surah 3 Al ‘Imran ayah 191 states: ‘Men who celebrate the praises of Allâh standing and sitting and lying down on their sides, and contemplate the wonders of creation in the heavens and on the earth, ‘Our Lord! Not for naught have you created all this, Glory to You! Give us salvation from the Penalty of the Fire.’ ’ In Surah 28 Qasas ayah 73 it states: ‘It is out of His mercy that he has made you night and day – that you may rest therein, and that you may seek his grace, in order that you may be grateful.’ The Qur’an confirms that through the creation of Allâh mankind would contemplate the existence of Allâh.