"Now the purpose of the commandment is love from a pure heart, from a good
conscience and from sincere faith." 1 Timothy 1:5

Using this verse we have looked into Scripture that speaks of love, a pure
heart and a good conscience, now let's look into 'from sincere faith'.

Faith here is the Greek word, PISTIS
VINE'S EXPOSITORY DICTIONARY tells us the following concerning PISTIS:
'...firm persuasion, a conviction based upon hearing, is used in the N.T.
always of faith in God or Christ, or things spiritual.
Vine goes on and "lists the MAIN ELEMENTS in faith in its relation to the
invisible God, as distinct from faith in man...'  They are:

'A firm conviction, producing a full acknowledgement of God's revelation or
truth.'
2 Thessalonians 2:10-12 tells of the result of not accepting the truth of
God,
"...They did not receive the love of the truth so as to be saved.  And for
this reason God will send upon them a deluding influence so that they might
believe what is false, in order they they all may be judged who did not
believe the truth, but took pleasure in wickedness."

'A personal surrender to Him.'
"But to as many as received Him, to them He gave the right to become
children of God, even to those who believe in His name." John 1:12

'A conduct inspired by such surrender.'
"We walk by faith not by sight."  2 Corinthians 2:7
Also see, Ephesians 4:1-3 where the Apostle Paul entreats us to walk
worthy of our calling.

A firm conviction of the truth; a personal surrender to Christ and a conduct
inspired by this surrender are all in contrast to just believing something
without reference to proof.

For me, the word 'believe' in John 3:16 in the Amplified Bible encompasses
these main elements:
"For God so greatly loved and dearly prized the world that He [even] gave up
His only begotten (unique) Son, so that whoever BELIEVES in (TRUSTS IN,
CLINGS TO, RELIES ON) Him shall not perish (come to destruction, be lost)
but have eternal (everlasting) life."  {My emphasis}

Let us then obey the commandment to unselfishly love with a heart that is
pure, a conscience that is clean and a faith that fully acknowledges God's
truth and is surrendered to God in Christ Jesus our Lord. Amen.