Messenger of Allah (PBUH) said, "Were this world worth a wing of mosquito, He would not have given a drink of water to an infidel."

[At- Tirmidhi, who classified it as Hadith Hasan Sahih].

that a man from the people of Al-'Iraq asked Ibn 'Umar about the blood of a gnat that gets on the clothes. Ibn 'Umar said "Look at this one, he asks about the blood of a gnat while they killed the son of the Messenger of Allah (SAW)! And I heard the Messenger of Allah (SAW) said: 'Indeed Al-Hasan and Al-Husain - they are my two sweet basils in the world.'"

A bulky person would be brought on the Day of judgment and he would not carry the weight to the eye of Allah equal even to that of a gnat. Nor shall We set up a balance for them on the Day of Resurrection" (xviii. 105).

‘Abdallah b. Unais reported God’s Messenger as saying, “Among the most serious of major sins are attributing a partner to God, unfilial behaviour, and deliberate perjury. If anyone swears an oath which he is compelled to take (or a firm oath) and introduces into it as much falsehood as a gnat’s wing, a spot will be put in his heart till the day of resurrection.” Tirmidhi transmitted it, saying this is a gharib tradition.

"If the world to Allah was equal to a mosquito's wing, then He would not allow the disbeliever to have a sip of water from it."

Ibn Abi Nu'm said, "I was with Ibn 'Umar when a man asked him about the blood of gnats. He asked, 'Where are you from?' 'From the people of Iraq,' he replied. He said, 'Look at this man! He asks about the blood of gnats when they murdered the grandson of the Prophet, may Allah bless him and grant him peace! I heard the Prophet, may Allah bless him and grant him peace, say, 'They are my sweet basil in this world.'"

“Allah the Blessed and Exalted says: ‘O My slaves, all of you are sinners except those whom I have saved. So ask Me for forgiveness, I will forgive you. Whoever among you knows that I have the power to forgive and asks Me to forgive by My power, I will forgive him. All of you are astray except those whom I guide. Ask Me for guidance and I will guide you. All of you are poor except those whom I enrich (make independent of means). Ask of Me and I will grant you provision. Even if your living and your dead, your first and your last, your fresh and your dry, were all as pious as the most pious among My slaves, that would not increase my dominion as much as a gnat’s wing, and if they were to be as evil as the most evil among My slaves, that would not detract from My dominion as much as a gnat’s wing. Even if your living and your dead, your first and your last, your fresh and your dry, were to join together and each of them were to ask for all that he wishes for, that would only detract from My dominion as much as if one of you were to pass by the edge of the sea and dip a needle in it and withdraw it. That is because I am the Most Generous, Majestic. I give with a word; when I will something, all I do is say to it “Be!” – and it is.’”

“We were with the Messenger of Allah (saw) in Dhul-Hulaifah, when we saw a dead sheep lifting its leg (because of bloating). He said: ‘Don’t you think this is worthless to its owner? By the One in Whose hand is my soul, this world is more worthless to Allah than this (dead sheep) is to its owner. If this world was worth the wing of a mosquito to Allah, the disbeliever would not have a drop to drink from it.’”

"Allah,Most High said: 'O My Slaves! All of you are astray except whom I guide, so ask Me for guidance and I shall guide you. All of you are poor except whom I enrich, so ask Me and I shall provide you. All of you are sinners except whom I have pardoned, so whoever among you knows that I am the One able to forgive, and seeks My forgiveness, I shall forgive him, without concern for Me (and it will not affect Me). If the first of you and the last of you, the living among you and the dead among you, the fresh among you and the dry among you were to gather together to help the heart with the most Taqwa among My slaves, that would not add a mosquito's wing to My sovereignty. If the first of you and the last of you, the living among you and the dead among you, the fresh among you and the dry among you were to gather together to help the worst heart of My slaves, that would not diminish a mosquito's wing to My sovereignty. I shall forgive him, without concern for Me (and it will not affect Me). If the first of you and the last of you, the living among you and the dead among you, the fresh among you and the dry among you were to gather together upon one plateau, and each person among them were to ask for his utmost desire, and I were to give each what he asked for, that would not diminish from My sovereignty, except as if one of you were to pass by an ocean and dip a needle into it and then remove it. That is because I am the Most Liberal without need, the Most Generous, doing as I will. I give by My speech and I punish by My speech, whenever I will something I only say: "Be" and it shall be.'"

Another chain reports a similar narration.

from 'Abdullah bin Unais Al-Juhni who said: "The Messenger of Allah (SAW) said: 'Indeed among the worst of the major sins is Shirk with Allah, disobeying the parents, the false oath, and none insists on taking an oath in which he swears, including the like of a wing of a mosquito (of falsehood) in it - except that a spot is placed in his heart until the Day of Judgement.'"

Abu Dharr reported God’s messenger as stating that God most high says, “My servants, all of you are astray except him whom I have guided, but if you ask me for guidance I will guide you; all of you are poor except him whom I have enriched, but if you ask of me I will give you provision; all of you are sinners except him whom I have preserved [from sin], but if any of you knows that I have power to pardon and ask my pardon I will pardon him, and I do not care; if the first and the last of you, the living and the dead among you, those of you who are fresh and those of you who are withered, 3 had all hearts as pious as the heart of the most pious of my servants, that would not add as much as a gnat’s wing to my dominion; if the first and last of you, the living and the dead among you, those of you who are fresh and those of you who are withered, had all hearts as wretched as the heart of the most wretched of my servants, that would not diminish as much as a gnat’s wing from my dominion; if the first and last of you, the living and the dead among you, those of you who are fresh and those of you who are withered, were gathered in one plain, each one of you asking all he could hope for, and I were to grant the request of each of you who asked, that would cause no more diminution in my dominion than if one of you passed by the sea and, after dipping a needle in it, took it out, that being because I am generous and glorious, doing what I wish. My giving is speech and my punishment is speech. My command to a thing when I want it is just to say to it ‘Be’ and it comes into being.” [cf. Qur’an, xvi, 40; xxxvi, 82.] 3. i.e., young and old. Ahmad, Tirmidhi and Ibn Majah transmitted it.