"This is the confidence we have in approaching God: that if we ask anything according to his will, He hears us. And if we know that he hears us - whatever we ask we know that we have what we asked of him" (1John:5:14-15).
'Have faith in God,' Jesus answered. 'I tell you the truth, if anyone says to this mountain, "Go, throw yourself into the sea," and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours. And when you stand praying, if you hold anything against anyone, forgive him, so that your Father in heaven may forgive you your sins'" (Mark 11:22-25)
And I will do whatever you ask in my name, so that the Son may bring glory to the Father. You may ask me for anything in my name, and I will do it" (John 14:13-14).
Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God. And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus" (Philippians 4:6-7)
The prayer of a righteous man is powerful and effective (James 5:16).
"And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints" (Ephesians 6:18).
In the same way, the Spirit helps us in our weakness. We do not know what we ought to pray for, but the Spirit himself intercedes for us with groans that words cannot express" (Romans 8:26).
"If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness" (1 John 1:9). Be joyful always; pray continually; give thanks in all circumstances, for this is God's will for you in Christ Jesus" (1 Thessalonians 5:16-18).
When you ask, you do not receive, because you ask with wrong motives, that you may spend what you get on your pleasures (James 4:3).